Can we digest food as well as herbivores

Can we digest food as well as herbivores

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I heard some guy say that we can't digest plant food as well as herbivores. Which seems weird to me seeing as how humans can survive without any nutrient deficiencies besides b12 on only plants but we would pretty much just die of nutrient deficiencies on a carnivore diet. Can someone show me how we can't digest plant food as well as herbivores?

Humans do not have microflora that can hydrolyze cellulose, but plant-eating herbivores do. One advantage of that though is that the cellulose helps move food through your gut and aids digestion. Herbivores have fermentation chambers in their alimentary canals that contain mutualistic bacteria and protists that can break down the cellulose for them; some of the microorganisms also use some of the sugars from the digested cellulose to produce nutrients vital to the animal, such as vitamins and amino acids. Also, herbivores have longer alimentary canals relative to their body size, due to the fact that plant matter is harder to digest because of the cell walls.

Here is an excerpt on herbivore teeth structure, taken from Campbell Biology, 10th Edition.

"Herbivores, such as horse and deer, usually have premolars and molars with broad ridged surfaces that grind through tough plant material. The incisors and canines are generally modified for biting off pieces of vegetation. In some herbivores, canines are absent" (Reece et al. 906).


  1. Reece, Urry, Cain, Wasserman, Minorsky, and Jackson. Campbell Biology. 10th ed. N.p.: Pearson, 2014. Print.

All animals, including humans, are adapted to life in a microbial world. Anaerobic habitats have existed continuously throughout the history of the earth, the gastrointestinal tract being a contemporary microniche. Since microorganisms colonize and grow rapidly under the favorable conditions in the gut they could compete for nutrients with the host. This microbial challenge has modified the course of evolution in animals, resulting in selection of complex animal-microbe relationships that vary tremendously, ranging from competition to cooperation. The ecological and evolutionary interactions between herbivorous dinosaurs and the first mammalian herbivores and their food plants are reconstructed using knowledge gained during the study of modern living vertebrates, especially foregut and hindgut fermenting mammals. The ruminant is well adapted to achieve maximal digestion of roughage using the physiological mechanism at the reticulo-omasal orifice which selectively retains large particles in the reticulo-rumen. However, the most obvious feature of all ruminants is the regurgitation, rechewing and reswallowing of foregut digesta termed rumination. Foregut fermenting mammals also share interesting and unique features in two enzymes, stomach lysozyme and pancreatic ribonuclease which accompany and are adaptations to this mode of digestion. The microbial community inhabiting the gastrointestinal tract is represented by all major groups of microbes (bacteria, archaea, ciliate protozoa, anaerobic fungi and bacteriophage) and characterized by its high population density, wide diversity and complexity of interactions. The development and application of molecular ecology techniques promises to link distribution and identity of gastrointestinal microbes in their natural environment with their genetic potential and in situ activities.

The gastrointestinal tract is a specialized tube divided into various well-defined anatomical regions extending from the lips to the anus. However, for the purposes of this contribution concerning mutualistic fermentative digestion, discussion is restricted to the stomach (rumen-reticulum, crop, gizzard), small intestine and large intestine (cecum and colon). By definition, foregut fermentors comprise animals with a pregastric fermentation chambers such as the rumen, reticulum, and omasum of ruminants and diverticula or fermentative sacs of other ruminant-like mammals. Hindgut fermentors are defined as those animals with large fermentation compartments in the cecum, colon and rectum. Large populations of microorganisms inhabit the gastrointestinal tract of all animals and form a closely integrated ecological unit with the host. This complex mixed, microbial culture comprising bacteria, ciliate and flagellate protozoa, anaerobic phycomycete fungi as well as bacteriophage can be considered as the most metabolically adaptable and rapidly renewable organ of the body which plays a vital role in the normal nutritional, physiological, immunological and protective functions of the host animal. Development of microbial populations in the alimentary tract of higher animals commences soon after birth. The processes involved in the establishment of microbial populations are complex, involving succession of microorganisms and many microbial and host interactions eventually resulting in dense, stable populations inhabiting characteristic regions of the gut.

Physical and chemical conditions within the gut of different animals may differ considerably but are usually relatively constant in a single species on a given diet. This is the case for homeothermic animals, in which, allowing for irregularities in the intake of food, factors such as temperature, oxygen, acidity and moisture vary little with time. In poikilothermic animals temperature can be a major variable.

The detailed composition of the gut contents of most animals is extremely complex. To date, the microbial environment in the rumino-reticulum has been closely defined and allowing for variation in the nature and amount of food ingested serves as a good model for other gut ecosystems, both herbivores and non-herbivores. The hindgut environment is more constant in terms of physical and chemical composition with nutrients for ceco-colonic bacteria being provided by undigested dietary polysaccharides and endogenous secretions and tissues such as mucopolysaccharides, mucins, epithelial cells and enzymes.

Can we digest food as well as herbivores - Biology

Unit Six. Animal Life

25. The Path of Food Through the Animal Body

Heterotrophs are divided into three groups on the basis of their food sources. Animals that eat plants exclusively are classified as herbivores common examples include cows, horses, rabbits, and sparrows. Animals that are meat eaters, such as cats, eagles, trout, and frogs, are carnivores. Omnivores are animals that eat both plants and other animals. We humans are omnivores, as are pigs, bears, and crows.

Single-celled organisms (as well as sponges) digest their food intracellularly, breaking down food particles with digestive enzymes inside their cells. Other animals digest their food extracellularly, within a digestive cavity. In this case, the digestive enzymes are released into a cavity that is continuous with the animal’s external environment. In flatworms (such as Planaria) and cnidarians, like the hydra in figure 25.3, the digestive cavity in the center of the body has only one opening at the top that serves as both mouth (the red arrow bringing food in) and anus (the blue arrow passing waste out). There can be no specialization within this type of digestive system, called a gastrovascular cavity, because every cell is exposed to all stages of food digestion.

Figure 25.3. Two-way digestive tract.

Food particles enter and leave the gastrovascular cavity of Hydra through the same opening.

Specialization occurs when the digestive tract, or alimentary canal, has a separate mouth and anus, so that transport of food is one way. Three examples are shown in figure 25.4. The most primitive digestive tract is seen in nematodes (phylum Nematoda), where it is simply a tubular gut lined by an epithelial membrane. Earthworms (phylum Annelida) have a digestive tract specialized in different regions for the ingestion, storage (crop), fragmentation (gizzard), digestion, and absorption of food (intestine). All higher animals, like the salamander, show similar specializations.

Figure 25.4. One-way digestive tracts.

One-way movement through the digestive tract allows different regions of the digestive system to become specialized for different functions.

The ingested food may be stored in a specialized region of the digestive tract or may first be subjected to physical fragmentation through the chewing action of teeth (in the mouth of many vertebrates) or the grinding action of pebbles (in the gizzard of earthworms and birds). Chemical digestion then occurs primarily in the intestine, breaking down the larger food molecules of polysaccharides, fats, and proteins into smaller subunits. Carbohydrate digestion begins in the mouth of some animals, and protein digestion begins in the stomach in some animals. Chemical digestion involves hydrolysis reactions that liberate the subunits—primarily monosaccharides, amino acids, and fatty acids—from the food. These products of chemical digestion pass through the epithelial lining of the gut and ultimately into the blood, in a process known as absorption. Any molecules in the food that are not absorbed cannot be used by the animal. These wastes are excreted through the anus.

Key Learning Outcome 25.2. Most animals digest their food extracellularly. A digestive tract with a one-way transport of food allows specialization of regions for different functions.

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Why can't herbivores eat meat, and why can't carnivores eat plants?

Is there a fundamental difference in the digestion process? Is it psychological? I know very little about animal anatomy or biology, but I would love to learn more!

Depends. The difference is very rarely psychological. The main difference is the digestive systems in place and the energy demands of the animal.

Deriving energy from plants is hard work thanks to cellulose and a whole heap of other barriers including poisons. Herbivores therefore either need to be specialists and focus on a handful of specific vegetation, or have most of their body devoted to processing nutrient poor but numerically plentiful food. The first strategy you can apply to, for example, squirrels, and the former to cows. In order for these systems to work they need specific enzymes to break down the food they are eating, and in the cow’s case several stomach portions and a whole regurgitating system for further breakdown. To further drive their food needs, their physiology has evolved to need energy and vitamins in proportions to what they typically eat. Even if meat is nutritionally more dense, a cow wouldn’t receive a great deal of benefit from it because a) Wrong enzymes to break down the food and b) the meat will have vitamins and minerals in wrong forms and proportions.

To add a further hurdles, having a multi-chambered, enormous digestive system, or other herbivore digestive demands such as grinding teeth, mean that you are poorly suited to catching prey.

Same goes for carnivores. They lack the enzymes or indeed the sheer length of digestive tract needed to break down plant matter, and their bodies require nutrients and minerals that can be obtained from prey. For example, cats have practically all their dietary demands in near perfect proportions in the form of mice.

What about omnivores? Well they have a grab bag of enzymes that can eat some plant matter but this is usually very easily digestible, such as berries or nectar. One of the earliest pre-requisites for civilisation was the design and harvesting of easily digested plant matter in the form of fruits, vegetables, and grain. Omnivores can also exploit meat thanks to enzymes, and their bodies are not so devoted to eating vegetables that they are hampered by the digestive systems. Omnivores tend to either need a heap of energy due to behaviour and size (such as overland migration) and be in areas where both plant and meat isn’t particularly plentiful. Occasionally you have omnivorous scavengers who simply exploit what they can.

As the word monogastric suggests, this type of digestive system consists of one (&ldquomono&rdquo) stomach chamber (&ldquogastric&rdquo). Humans and many animals have a monogastric digestive system as illustrated in Figure (PageIndex<5>). The process of digestion begins with the mouth and the intake of food. The teeth play an important role in masticating (chewing) or physically breaking down food into smaller particles. The enzymes present in saliva also begin to chemically break down food. The esophagus is a long tube that connects the mouth to the stomach. Using peristalsis, or wave-like smooth muscle contractions, the muscles of the esophagus push the food towards the stomach. In order to speed up the actions of enzymes in the stomach, the stomach is an extremely acidic environment, with a pH between 1.5 and 2.5. The gastric juices, which include enzymes in the stomach, act on the food particles and continue the process of digestion. Further breakdown of food takes place in the small intestine where enzymes produced by the liver, the small intestine, and the pancreas continue the process of digestion. The nutrients are absorbed into the blood stream across the epithelial cells lining the walls of the small intestines. The waste material travels on to the large intestine where water is absorbed and the drier waste material is compacted into feces it is stored until it is excreted through the rectum.

Figure (PageIndex<5>): (a) Humans and herbivores, such as the (b) rabbit, have a monogastric digestive system. However, in the rabbit the small intestine and cecum are enlarged to allow more time to digest plant material. The enlarged organ provides more surface area for absorption of nutrients. Rabbits digest their food twice: the first time food passes through the digestive system, it collects in the cecum, and then it passes as soft feces called cecotrophes. The rabbit re-ingests these cecotrophes to further digest them.


The collective processes by which a living organism takes food which are necessary for their growth, maintenance and energy needs is called nutrition. The chemical substances present in the food are called nutrients.
It is important to know the different modes of nutrition in all living organisms in order to understand energy flow within the ecosystem. Plant produces high energy organic food from inorganic raw materials. They are called autotroph and the mode of nutrition is known as autotrophic nutrition. Animals feed on those high energy organic food, are called as heterotrophs and their mode of nutrition is known as heterotrophic nutrition.
Heterotrophic nutrition further sub-categorise in holozoic, parasitic, and saprophytic
mode of nutrition based on the pattern and class of food that is taken inside.
Holozoic Nutrition: It involves taking entire organic food and this can be in the form of whole part of plant or animal. Most of the free-living protozoans, humans and other animals fall into this category.
Saprophytic Nutrition: The organism fulfils the requirement of food from the rotten parts of dead organisms and decaying matter. The organisms secrete digestive enzymes outside the body on their food and then take indigested food. It is a kind of extra-cellular digestion. Examples: Housefly, Spiders etc.
Parasitic Nutrition: The organism fulfils the requirement of food from the body of another organism. The parasites are of two distinct types, one which lives inside the host and the other which lives outside. The internal parasites usually multiply inside the body cavity of host and most of the times are life-threatening while the other lives outside and can play the role of vectors in spreading diseases. Example of internal parasites is Plasmodium, tapeworms etc. while the example of external parasites may include mostly fleas and insects.


Ingestion: The act of taking food inside by the organisms is called ingestion. Most of the animals consume solid food, excepting a few (mosquitoes, flies and spiders suck in liquid food). Different animals use different organs for this purpose. For example Amoeba, a unicellular organism can ingest food from its body surface. In Hydra, the food is taken inside with the help of tentacles. In vertebrates like frogs, birds and mammals, well-developed organs and methods are present to ingest food.
Feeding involves procurement as well as ingestion of food. Depending upon the nature of food, feeding may be of three types in animals.
Microphagy: This method is also known as filter feeding. Food particles smaller in size pass through filter along with water. The food particles are trapped and utilized whereas water is removed from the body. Examples of organisms which show microphagy are paramecium, sponges, crustaceans, certain fishes and birds, blue whales, etc.
Macrophagy: This method involves the feeding of food particles which are large in comparison to the size of the organism. Organisms swallow whole food without chewing. Example of organisms which shows macrophagy are amoeba, hydra, certain amphibians, reptiles, fishes and birds.
Liquid feeding: Leeches, tape-worm, mosquitoes, bugs, spiders, flies, bats and milf sucking young mammals shows different feeding behaviour where they ingest liquid
food, known as liquid feeding or fluid-feeding.
We have listed some mode of feeding that organism exhibits

  • Filter feeding: feeding particles suspended in water.
  • Deposit feeding: feeding particles suspended in the soil.
  • Bulk feeding: feeding all of an organism.
  • Fluid feeding: feeding fluid of other organisms.
  • Ram feeding and suction feeding: ingesting food particles via the fluids around it.

Mechanism of ingestion in unicellular organisms (such as amoeba)

When food particles come in contact with the cell surface of amoeba, it slowly engulfs the whole food with the help of pseudopodia. This process takes place in approximately 2 min.
Different modes of ingestion reported in amoeba are as follows:

  • Circumvallation: With the help of pseudopodia food cup form to engulf active
    prey like Paramecium.
  • Circumfluence: Amoeba rolls over the inactive prey.
  • Import: Food particles like algal filaments passively sink into the body when it comes in contact.
  • Invagination: A sticky and toxic substance is secreted by pseudopodia, which kills the prey and then taken by invagination
  • Pinocytosis: Certain channels present on the body surface of the amoeba to ingest liquid food.

Digestion of food in Unicellular Organism (Amoeba):

Ingested food remains in the food vacuole. The food vacuole is then transported deeper into the cytoplasm where they fuse with lysosome that contains amylase and certain proteinases. After digestion, solid food is converted into liquid diffusible form and readily absorbed by cytoplasm through diffusion process. The undigested food is egested by exocytosis. The complete steps of nutrition are shown in Figure

Steps of Digestion in Amoeba

Mechanism of Digestion in the multi-cellular organism (such as Hydra)

Hydra is a freshwater diploblastic animal. It’s body composed of two layers. Outer layer is protective and sensory epithelium and the inner layer is gastrodermis act as a nutritive epithelium. The central body cavity is known as coelenteron act as the digestive tract.
Hydra catches the prey with the help of tentacles, a protrusion just outside the mouth. The circumference of mouth can extend according to the size of food particle. Thus it can swallow comparatively large animal. Soon after ingestion, digestion process starts with the help of enzymes secreted by granular glands, which appears just after ingestion. The undigested food is then egested through the mouth. The complete mechanism of nutrition in hydra is shown in Figure

Steps of Digestion in Hydra

Mechanism of Digestion in sponges:

Sponges don’t have the distinct digestive system. They engulf food by the support of water flow system. They show filter-feeding behaviour, where food particle filters out of the water passing through them. Only particle smaller than 50 micrometres can enter through ostia. Sponges consume food by phagocytosis with the help of pinacocytes or
archaeocytes. Food particles smaller than 0.5 micrometres can catch and consumed by

Mechanism of Digestion in Lower Vertebrate such as Cockroach

Cockroach searches the food with the help of antennae, maxillary and labial palps. These appendages bear sense organs. With the help of labium and labrum, the pro-legs pick up and bring food to the pre-oral cavity. Mandibles contain teeth which help in mastication of food in a pre-oral cavity. The lacinia present in the maxillae also helps in mastication. The food is mixed with saliva in a pre-oral cavity. The saliva of cockroach contains amylase, chitinase and cellulose which digest carbohydrate partially in a pre-oral cavity. Food from the pre-oral cavity is then transported to esophagus and then into the crop. Crop is analogous to the stomach of human, which store food for some time and also digestion takes place. Then food reaches to gizzard for crushing into fine particles, which then passes to midgut. Most of the digestion carried out in the midgut. Digested food is absorbed by the inner lining of midgut through diffusion. The undigested food passes to hindgut. Water and electrolytes absorb here and the undigested liquid food is converted to semisolid faeces, which the passed out through anus in the form of small dry pellets. The complete digestive system of cockroach is shown in Figure

Digestive System of Cockroach

Biology Notes Life on Earth + Digestive System Essay

Topic: patterns in nature Compare the digestive systems of mammals. Include: grazing herbivore, carnivore and a predominantly nectar feeding animal Major parts of mammalian digestive systemsgrazing herbivore GOAT carnivore CATpredominantly nectar feeding animal HONEY-POSSUM Mouth- no incisor or canine teeth – depend on firm dental pad in front of hard palate, lower incisors, lips, and tongue to take food into mouths – use molar teeth to grind food to increase surface area so that it is more exposed to digestive chemicals that help to break it down.

These molars are used again to chew even further when the cud is regurgitated. – mouth of a cat contains a pharynx, soft palate, hard palate and variety of teeth (incisors, canine, premolars and molars) – takes its food in with teeth and lips – Some chew the pieces, others swallow them whole – saliva moistens food so it is easier to swallow tongue pushes food back through the pharynx into the esophagus – tongue has range of papillae, including filiform (doesn’t contain taste buds), fungiform, vallate and foliate- elongated snout and long tongue covered in papillae that collect the pollen – tongue moves in and out of mouth 2-3 times a second and is supported by the teeth, which are all very tiny, except for the two front teeth in the bottom jaw which act as main supporters for the tongue – When tongue re-enters the mouth it scrapes against roof of mouth which contains ridges that scrape off the pollen Teeth- no upper teeth incisor or canines teeth they use are lower incisor teeth, along with the dental pad in front of the hard palate, tongue and lips which are all depended on to take food into mouth- mouth of a cat contains a variety of different teeth: Canines– grab, hold & tear prey Incisors– scrape meat off bones Molars and premolars– crush meat so it is easier to swallow See picture 1- only a few, tiny teeth – incisors and canines are narrow and pointed – cheek teeth flat with round tips – lack of strong teeth because of no need to bite or crush food See picture 6

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Esophagus- tube-like passageway from mouth to stomach – opens into the stomach at the point where rumen and reticulum meet – helps transport both gases and cud- begins at end of pharynx, continues down neck next to the trachea, through diaphragm, finally connecting with the stomach – first passageway in digestive system, so often exposed to rough food which has not been fully chewed i. e. pieces of bone – surface therefore has to be resistant to damage, so is lined with stratified squamous epithelium.

See picture 2- simple tube that moves food from mouth to stomach – At entry from esophagus to stomach the lining of the esophagus changes from stratified squamous (picture 2) to tall column shaped cells StomachGoat’s stomach has four compartments (see picture 3): 1) rumen: largest compartment. Here food is moistened and churned around to break down into smaller pieces Capacity: 11 -22 litres depending on food eaten 2) honey-combed reticulum: located just below entrance from esophagus into stomach.

Part of the rumen, only separated by thin fold. Bacterial cellulases act on food here and food is made into round balls called cud which is regurgitated into mouth and chewed into small particles. Capacity: 1-2 L 3) omasum: after cud has been regurgitated and cellulose broken down, it is re-swallowed and moves into the omasum, consisting of layers of tissue that grind up cud and remove some water from it.

Capacity: approx 1L 4) abomasum ‘true stomach’: functions similarly to human stomachs. Contains hydrochloric acid and enzymes that break down food particles before entering small intestine. Capacity: approx. 4L- stomach of a cat is designed to store large amounts of food and begin digestive process – esophagus carries food into the stomach, where it enters through a valve called the cardiac sphincter – lining of stomach has many folds called gastric folds, which elp crush and grind food – stomach lining also secretes acids and enzymes which break down the food – Once stomach digestive process is done, the partly digested food exits the stomach through the pyloric sphincter area and then enters first part of the small intestine (duodenum) – Most food leaves the cat’s stomach within 12 hours after entering- two chambers: the main chamber and the diverticulum (the smaller chamber) – stomach wall is lined with ridges and also epithelial cells which produce mucus, but no pepsinogen is secreted so no protein is digested in the stomach – stomach merely acts as a storage place for nectar and pollen Small intestine- as partly digested food enters first part of small intestine (duodenum), enzymes produced and secreted by the pancreas break down nutrients from food into simple compounds – These compounds are absorbed mainly from the jejunum and ileum (2nd and 3rd part of small intestine), into the blood stream – lining of wall is covered in many small fingerlike projections called villi see picture 4, which increase surface area for absorption- small intestine is lined with villi (for larger surface area for absorption) see picture 4 – has blood vessels which take nutrients to other parts of the body – three sections: duodenum, jejunum and ileum Duodenum – section where Jejunum – largest part of small intestine, section where most of the absorption takes place Ileum – final section of small intestine, where absorption process ends- Honey-Possum lacks a Caecum, which makes it difficult to identify where small intestine finishes and where large intestine starts – we do know that pollen is digested in both the small and large intestines. Caecum- located at point where small and large intestines meet – Digestion in caecum is done by microorganisms which break down the cellulose fibres in plant material. – caecum of a goat can hold up to 1 litre! small, comma-shaped pouch which hangs just below the point where the ileum meets the large intestine – compared to most carnivores, caecum of a cat is very small, and its function is unknown- Honey-Possum does not actually have a caecum Large intestine- Undigested food and unabsorbed nutrients leaving small intestine move into large intestine – functions include water absorption and further digestion of food by microorganisms – large intestine of a goat is made up of the colon and rectum- large intestine connects the small intestine to the anus – larger in diameter than small intestine, but shorter in length – made up of caecum, rectum and colon (longest section) Main functions are water absorption, keeping the body’s hydration level constant, and to store faeces waiting to leave the body- Honey-Possum has no Caecum, which makes it hard to tell where small intestine finishes and large intestine starts – we do know that pollen is digested in both small and large intestines – faeces waiting to leave body is stored at the end of the large intestine Digestive juices and Enzymes- Enzymes secreted by pancreas are important in digestion of carbohydrates, proteins and fats – Bile produced by liver and stored and secreted by gall bladder helps soften the fat particles in preparation for digestion – stomach contains bacteria and protozoa which break down cellulose walls, as well as hydrochloric acid, pepsin and lipase which break down plant proteins and fats- As food passes into stomach, the stomach lining secretes acids and enzymes needed to break down food – pancreas and liver supply enzymes needed to break down fats and proteins so they can enter into blood stream – Bile that is stored in the gall bladder is mixed with the food in the duodenum to chemically break down food even further- honey possum’s stomach produces mucus from the epithelial cells that cover lining of the stomach wall. However, this mucus contains no protein digesting enzyme (pepsinogen) Faeces- Goat faeces are formed in end part of the colon – comes out as small, dry pellets. See picture 5- faeces of a cat is stored in end section of large intestine called the rectum – colour and texture varies depending on cat’s diet- Almost all pollen grains that are excreted in faeces are empty, as the content of the pollen is digested in stomach and intestines Why are they different? Mouth + Teeth The main difference in the mouths of the mammals’ digestive systems are the teeth.

The teeth differ according to the diet of the animals. The grazing herbivore only eats plants, so their teeth are designed to grind the food to increase the surface area, whereas the carnivore eats meat, so the main function if its teeth is to grab, hold and tear the prey, scrape meat off bones, and then finally crush the meat before swallowing. Lastly, the nectar feeding mammal barely uses its tiny teeth, as the tongue collects the pollen and scrapes it against the roof of the mouth, so no chewing or tearing is involved. Esophagus The esophagus of the different types of mammals acts quite similarly, mainly just functioning as the passageway from the mouth to the stomach. Stomach

A grazing herbivore eats only plants, in which cellulose is very difficult to break down, so they therefore have a four chambered stomach so that the food can be partly digested and then regurgitated and moved into the next stomach so that the cellulose can be properly broken down. The carnivore only has one stomach which begins the chemical breakdown process of the meat. Meat is not as complex to digest as plant matter, which is why only one stomach is needed. The nectar feeding mammal has a two chambered stomach, which produce mucus, but the stomach mainly acts as a storage place for nectar and pollen, with most of the digestion being done in the small intestine. Small intestine The small intestine of the grazing herbivore and the carnivore are quite similar.

Both of these small intestines take nutrients into the body through the blood stream and are both lined with villi to increase surface area for absorption. Also, they both have three sections called the Duodenum, Jejunum and Ileum. The nectar feeding mammal’s small intestine also absorbs nutrients into the blood stream, but as they lack a caecum, it is difficult to tell where the small intestine ends and the large intestine starts. Caecum The caecum in a grazing herbivore is quite large, and is very important in the digestive process, as cellulose fibres are broken down here. This is very different to the caecum of a carnivore, which is very small and has an unknown function. A nectar feeding mammal lacks a caecum altogether, as there is no need for it in the digestion process. Large intestine

Water absorption and further digestion is common in the large intestines of both the grazing herbivore and the carnivore, whereas almost all of the digestion of pollen and nectar is done in the small and large intestines of the nectar feeding mammal. In all three mammal types, the end of the large intestine is used to store the faeces before it leaves the body. Digestive juices and Enzymes The digestive juices of the three types of mammals are different because of their different diets. Grazing herbivores eat plants, therefore their stomachs contain bacteria and protozoa to break down the cellulose walls, as well as acids and enzymes to break down the plant proteins and fats. Their pancreas also secretes enzymes to break down carbohydrates, proteins and fats.

The carnivore’s pancreas and liver supply the enzymes to break down fats and proteins of the meat they eat. Their stomach lining also secretes acids and enzymes needed to break down the meat. The nectar feeding mammal’s stomach produces digestive mucus, however this mucus contains no pepsinogen, as most of the digestion of protein from the pollen is done in the intestines. Faeces Faeces of the different types of mammals are stored in the rectum but are all very different due to the different diets. Faeces of a grazing herbivore come out as small, dry pellets, due to their diet of plant matter and all the water absorption that takes place in the large intestine.

A carnivore’s faeces vary in colour and texture, as their diet often changes between different species and breeds. When a nectar feeding mammal’s faeces is excreted, the pollen grains are empty, as the content of the pollen has been digested in the stomach and intestine to provide the nutrients needed for the animal to survive. Topic: life on Earth Describe the experiments of Urey and Miller and use available evidence to analyse the: a)Reason for their experiment(s) b)Result of their experiment(s) c)Importance of their experiment(s) in illustrating the nature and practice of science (i. e. scientific method) d)Contribution to hypotheses about the origin of life (supported? Refuted? )

In 1953 Professor Harold C. Urey of the University of Chicago and his graduate student Stanley L. Miller created an experiment to test the hypothesis made by Oparin and Haldane which stated that ‘organic chemicals were produced from non-living matter on the early Earth’ – Biology in Context. Miller set up a series of glass tubes and flasks connected in a loop with a lower chamber of water representing oceans and an upper chamber representing the atmosphere. The liquid was heated to make evaporation occur and electric currents were passed through the atmosphere chamber to simulate energy such as lightning that is thought to be common in the early atmosphere.

The atmosphere was then cooled so that the water could condense and slowly return back into the first flask and the cycle would begin again. The tests were carried out for one week and at the end of the week Miller and Urey observed that 10-15% of the carbon had formed organic compounds and 2% of the carbon had formed amino acids (including glycine and alanine) that are used to make proteins. Sugars, lipids and some of the building blocks for nucleic acids were also formed. a)Reason for their experiment(s) The purpose of Urey and Miller’s experiment was to investigate whether it would be possible for non-living matter to create organic chemicals under the conditions thought to be present in the early Earth.

They essentially designed their experiment to test the hypothesis made by Oparin and Haldane. The experiment was designed to simulate conditions of the unstable early Earth and to test for biological chemicals. b)Result of their experiment(s) Urey and Miller’s experiment proves that certain organic compounds such as amino acids, could be made under the conditions that scientists considered to be present on early Earth. However, the experiment does not prove that this is how life began or that this is the way those particular compounds were created either. It also does not prove that early Earth was how Oparin and Haldane suggested it. c)Importance of their experiment(s) in illustrating the nature and practice of science (i. e. cientific method) The scientific method is a process used when designing and carrying out an experiment. The first step is to ask a question about something that you observe, then to do background research on the topic. After this you must construct a hypothesis, test it with an experiment and record your results. You must then draw a conclusion and state whether your hypothesis is true or not. Urey and Miller’s experiment illustrates the nature and practice of science through their thorough use of the scientific method. They took the hypothesis of Oparin and Haldane and developed a controlled experiment to test whether this hypothesis could be correct.

After researching their idea they came up with the best way to experiment to get the most reliable results. After performing their experiment, they clearly recorded the data that they came up with without changing it. Their experiment was reproducible so that others can try it and come up with the same results. Although the results of their experiment are often argued over by different scientists around the world, Urey and Miller have created a stable base for further research into the origins of the Earth. d)Contribution to hypotheses about the origin of life (supported? Refuted? ) There are many theories about the origin of life. One theory – Spontaneous Generation – supports the idea that life spontaneously arises from non-living matter.

This theory was accepted as ‘fact’ until it was scientifically tested by Francesco Redi in 1668, who discovered that maggots came from eggs laid by flies and did not just spontaneously arise. But it was not until 1862 that people stopped believing in spontaneous generation when Louis Pasteur convinced them that it does not occur. Another theory is that our DNA and RNA come from outer space and arrived here during the time of early Earth. A third theory is that life came from non-living matter on early Earth. This theory began from a hypothesis made by two scientists, Oparin and Haldane, but was not actually tested until 1953 by Miller and Urey.

Urey and Miller contributed greatly to Oparin and Haldane’s hypothesis of the origin of life, as they were the first to actually test it. Their experiment half supported the hypothesis, as it proved that it is possible for non-living matter to produce organic chemicals under specific conditions. But it did not completely support the hypothesis, as their experiment did not prove that this was how life on Earth began, or that early Earth was how Oparin and Haldane suggested it. Urey and Miller’s experiment significantly contributed to Oparin and Haldane’s hypothesis of the origin of life, and provided a base for further investigation of this theory.

The digestive system consists primarily of the alimentary canal, a tube that extends from the mouth to the rectum. As food moves through this canal, it is ground and mixed with various digestive juices. Most of these juices contain digestive enzymes, chemicals that speed up reactions involved in the breakdown of food. The stomach and the small intestines, which are parts of the alimentary canal, each produce 3 digestive juice. Other digestive juices empty into the alimentary canal from the salivary glands, gall bladder, and pancreas. These organs are also part Of the digestive system.Part 1 Location of the parts.

The Digestive TrackThe BIG MAC is placed in the mouth. The bread is mainly starch, the specialsauce is mainly fat, lettuce, pickles, and onions are niacin. The beef pattiesare protein,and cheeseis a form of calcium, fat, and protein. The piece of the BIG MAC is placed in the mouth and chewed, the starch isbeing digested by saliva. The starch becomes a kind of sugar which is used as anourishment for the cells. Saliva changes food to a form that can be used bythe body called enzymes. The burger is swallowed and passes into the esophagus. This is the muscular tube.

It is in the mouth, that the Thanksgiving feast begins its journey through the fabulous digestive system. It is here that the lips, cheeks and tongue, carefully position the food that the teeth will chew. This chewing process breaks up the food, this being a part of mechanical digestion. While the teeth grind up the turkey and tasty stuffings, the salivary glands begin emitting enzymes, these enzymes being contained in saliva. This saliva helps to dissolve some foods, and adds mucus to make the food's passage through the digestive system a little more "speedy". The saliva also attacks dangerous microorganisms.

THE DIGESTIVE SYSTEM OF THE FROG The digestive organs are usually divided into two main groups. The gastrointestinal tract or the alimentary tract and The accesory organs. The gastrointestinal tract (alimentary tract) -is a continuous tube running from the mouth to anus. This compose of mouth, parynx, esophagus, stomach, small intestine and large intestine. The accesory organs -is a group of organs consist of organs such as the teeth, tongue, liver, gallbladder and pancreas. *Place the preserved frog in a dissecting pan. open its mouth and study the roof and the floor of the mouth. may be necessary to cut.

Digestive SystemThe human body uses various kinds of food for energy and growth. To be used, however, food must be changed into a form that can be carried through the bloodstream. The body's process of extracting useful nutrients from food is called digestion. The digestive system of humans and other higher animals is the group of organs that changes food--carbohydrates, fats, and proteins--into soluble products that can be used by the body. Both mechanical action and chemical action are necessary to change food into products that are usable by the body. Human digestion, or the change that food undergoes in.

QuestionAnswer abomasum last section of the ruminant stomach that acts as the true stomach and allows food to be digested alimentary canal veterinary medical terminology for the GI system amylase enzyme produced by the pancreas that breaks down starches anastomosis surgical removal of a dead area of tissue along the digestive tract and resectioning the areas back together ascending colon first section of the large intestine avian system specialized digestive system of birds beak avian mouth with no teeth that forms an upper and lower bill bile yellow fluid that helps break down food for digestion and absorption of food.

QuestionAnswer 1. Air is killed by: Acid in the stomach 2. Bile is made by: Liver 3. Bile is stored in: Gallbladder Chief cells produce: pepsinogen and chymosin 4. Parietal cells produce: gastric acid 5. Where most digestive absorption occurs: small intestine 6. Which intestinal hormone stimulates contractions within the walls of the gallbladder and pushes bile into the small intestine: cholecystokinin (cck) 7. Enzymes from the ________ do most of the digestive work in the small intestine: Pancreas 8. Microvilli, Plicae and intestinal villi: increase the absorptive surface area of the small intestine 9. Chemical Digestion of fat is.

subject = biologytitle = Biology InstinctInsects are neumeroutinvertebrate animals that belong in the Phylum Arthropoda and Class Insecta. The class Insecta is divided into 2 subclasses: Apterygota, or winglessinsects, and Pterygota, or winged insects. Subclass Pterygota is futher dividedon basis of metamorphosis. Insects that have undergone incomplete metamorphosisare the Exopterygota. Insects that undergo complete metamorphosis are theEndopterygota. Insects have an outer bilateral exoskeleton to which themuscles are attached to and provides protection for internal organs. Thebody is divided into 3 main parts which are the head, which include mouthparts,eyes, and antennae thorax, which operate the jointed legs and /or wingsand.

It’s a typical day. After school you get home and you are starving, but you just want a snack. “What should I eat?,” you ask yourself. Then, after looking through the cabinets for a few minutes, you find Cheetos and decide to eat a few. With just the presence of those Cheetos in your sight, the digestion process begins in your 9 meter long digestive tract. Crunch, Crunch, Crunch. As you munch on those first few Cheetos the digestion process begins in your mouth. Here, mechanical digestion begins to reduce the size of the Cheeto and mixes the food particles.

Which parts of the flowers are important in pollination? Describe their role in the process, Pollen is produced in the stamen, pollination occurs when that pollen is transported from the anther to the style by insects or animals that are attracted to the plant by the beautiful petals of the flower. 2. Which parts of the flower are involved in fertilization and fruit development? Fertilization starts after pollination has occurred, and begins inside the pistils. The ovule contained inside the ovary is fertilized and the ovule begins to harden and form into a seed to protect the embryo until it.



Another function of Hydrochloric Acid is to kill any bacteria which may enter the stomach. (digestive system) Mucus helps to protect the stomach wall from its own secretion of Hydrochloric acid. If Mucus is not secreted ,hydrochloric acid will cause the erosion of inner lining of stomach leading to the formation ulcers in the stomach.


The partially digested food then enters into the small intestine. it is the site of complete digestion of food. The small intestine receives secretion of liver and pancreas. The wall of small intestine contains glands secreting intestinal juices. All these secretions completes digestion of carbohydrates (into glucose), fats (into fatty acid and glycerol) and proteins (into amino acids) In this way, the process of digestion converts the large and insoluble food molecules into small and water soluble molecules. (digestive system) The chemical digestion of food is brought about by biological catalysts called Enzymes.




Unmodified humans can survive on a animal-only diet (see: Inuit diet). Turning humans into obligate carnivores would require removing the digestive enzymes for dealing with plants, but would not require any changes to the large-scale anatomy.

Humans who evolved from an obligate-carnivore ancestry would likely have differently-shaped teeth, with the incisors better adapted for dealing with meat, but this would not be the case with humans who recently lost the ability to digest plant matter (the advantage of more efficient teeth is only a minor one, and does not provide a strong evolutionary pressure).

If humans had evolved to be obligate carnivores, then there would be some differences in dentition and digestive system, as well as possibly in our hands and feet.

A carnivore's dentition is, put simply, sharper. Incisors tend to be pointier, there are typically long, pointed canines (rather than the small, typically blunted set humans have), and instead of molars, there are carnassials, teeth designed to cut flesh like a pair of scissors. A carnivore does not need to grind their food, as meat is easily digested even if it is swallowed in relatively large lumps. Their dentition is designed to separate meat from bone and to reduce it to a size that can be swallowed as rapidly as possible.

An obligate carnivore has a large stomach that is used to store as much meat as possible, making a meal last as long as possible. The effort needed to digest meat is relatively low, and carnivores have shorter intestines than omnivores.

An obligate-carnivore human's belly might not look too much different to that of a normal human, perhaps flatter when hungry, and more bulging after a meal. They may eat only once each few days rather than several times each day.

Hands and feet:

Carnivores tend to have claws to facilitate the capture of prey. An obligate carnivore human may have claws rather than nails on their fingers and toes to facilitate capture of prey. Such a beings limbs would likely also be more heavily muscled, as they may be required to hang on to struggling prey animals - the disadvantage with carnivory is that the meal can fight back. This may also mean that the skin would need to be tougher.

Some carnivores have very strong jaws to facilitate cracking bones to extract marrow, however for tool-using humans, this can be achieved with the expedient of being able to grip bones and smash them against a hard surface, or by pounding on them with rocks. Hence, such human-like carnivores would make good scavengers too.

Can we digest food as well as herbivores - Biology

If all animals were created herbivores, why do many now eat meat?


In Genesis 1:29, it is clear that plants were the given food for all animals at the beginning of the creation, and it is only following the flood that we were instructed to eat animals. God originally designed us to eat plants, however because of Adam's sin, God cursed the creation, and this principally affected plants as a ready food source. The Bible states that the curse caused the plants to change and bare thorns, and there began an immediate requirement for humans to farm crops to obtain enough food to survive.

The world was designed with producers (plants) and consumers (animals). We were designed to eat plants, and the world is completely covered with such organisms, but people will starve without farmed crops. The nature of the curse upon Adam lies within the explanation of this dilemma. We use sugar as the fuel source that is used to make energy, and plants were designed to make this sugar in massive quantities. However, we can digest none of this energy, but instead it passes through us as dietary fiber. Given the description of the curse, it is theoretically possible all organisms were originally able to digest plant fiber, and we cursed to be unable.

God Giving Plants for Food - Genesis 1:29-30 And God said, "Behold, I have given you every plant yielding seed which is upon the face of all the earth, and every tree with seed in its fruit you shall have them for food. And to every beast of the earth, and to every bird of the air, and to everything that creeps on the earth, everything that has the breath of life, I have given every green plant for food." And it was so.

The Creation Cursed - Adam Must Farm Plants - Genesis 3:17-19 And to Adam he said, "Because you have listened to the voice of your wife, and have eaten of the tree of which I commanded you, 'You shall not eat of it,' cursed is the ground because of you in toil you shall eat of it all the days of your life thorns and thistles it shall bring forth to you and you shall eat the plants of the field. In the sweat of your face you shall eat bread till you return to the ground, for out of it you were taken you are dust, and to dust you shall return."

Genesis 3:23 - therefore the LORD God sent him forth from the garden of Eden, to till the ground from which he was taken.

Evolution of the Carnivore

It is now well recognized that all carnivores are actually omnivores by nature. Bears for example eat everything, but it was probably their sharp teeth more than anything that caused them to be originally labeled as a carnivore. Evolution is the process of specializing to a particular habitat or niche through a history of genetic recombination and natural selection. This process modifies the characteristics common to the organism in a manner which supplies regional specificities. The panda bear is an obligate herbivore. On the other hand, the polar bears are exclusively carnivore, but the bear was created as a vegetarian. All modern carnivores were originally herbivores that have adapted to predatory behaviors in some instances.

Plants use carbon dioxide and energy from the sun to make carbohydrates or sugar. Virtually all of the sugar made by the plant is polymerized into a long chain called cellulose or what we call "fiber". The plant uses cellulose primarily to make the cell wall which provides the plant's structural support. We alternatively metabolize carbohydrates to release the energy stored in the chemical bonds, and use it for moving muscle, or enzymatic reactions like making protein. There are many forms of sugar (glucose, sucrose, fructose, etc., but all of them are converted into glucose before they are used to make most of our ATP energy. Cellulose is simply a long chain of pure glucose, and yet we can not metabolize this most abundant form of energy.

Cellulose Fiber

We can not digest cellulose because we lack the necessary genes, and can not make the enzymes cellulase, lignase, etc. Only the microbial decomposers (bacteria, fungi) possess these genes . From an evolution standpoint the absence of these genes in higher organisms is a mystery if animals truly evolved from microbes since they all have the ability to digest cellulose. The survival advantage of these genes is so great that natural out-selection is inconceivable. If we evolved from microbes, we should also have these same genes.

Cellulose is without a doubt the single most abundant energy source on earth, but no consumer can not digest it. Instead the energy we get from plants comes almost exclusively from reproductive growths where starch and simple sugars are stored. Roots are also frequently rich in starch. However, it is because of our inability to digest cellulose that we must farm and produce massive quantities of plants, and then only harvest a very minor portion for consumption. Cellulose is virtually everywhere we look. It surrounds every plant cell, and yet we can make no use of it.

It is inexplicable that we and the animals are unable to utilize the massive quantity of energy which is trapped in cellulose being that we were created to eat plants and many still diet exclusively on vegetation. Ruminants (cow, sheep, etc.) possess a cooperative system which utilizes the enzymatic capability of bacteria to aid in the digestion of cellulose, otherwise no herbivore is able to digest this most abundant polysaccharide on earth. If we could digest cellulose, it would release more energy-producing metabolites than any other source available to us, and yet it is biochemically locked. From an intelligent design perspective, we should have the ability to digest cellulose. If we did, not one organism on earth would ever have starved, instead mass amounts of biochemical energy rot on the ground each year.

Although fruit is obviously a perfectly designed food, it is also seasonal, and was probably created with simple sugars only to be a candy that would promote seed transport. It is however logical to assume we would have been created with the ability to digest cellulose as our primary staple in the beginning. Theoretically, the curse might have involved the removal of these necessary genes from humans and all animal forcing us to labor endlessly to obtain enough usable carbohydrate, and causing many to evolve to carnivorous diets to survive.

If we could digest cellulose we would not need to farm to survive. We would be able to live for many days off the energy stored in a small bowl of any part of a plant (grasses, trees, etc.) Instead almost none of the glucose in basic roughage is metabolized, but instead it passes through as undigested fiber. This is a true waste of the stored energy in these foods, and a puzzle from the ID perspective unless this inability is related to a curse subsequent to our creation.

Given Animals as Food After the Flood - Genesis 9:2-3 The fear of you and the dread of you shall be upon every beast of the earth, and upon every bird of the air, upon everything that creeps on the ground and all the fish of the sea into your hand they are delivered. Every moving thing that lives shall be food for you and as I gave you the green plants, I give you everything.

by Chris W. Ashcraft