Nutrient Acquisition by Animals

Question 1

Four Steps of Digestion

Answer 1

animals are CHEMOHETEROTROPHS - must obtain both energy and carbon from pre-existing organic molecules; they do this by digestion:
1. Ingestion
2. Digestion
3. Absorption
4. Elimintation

Question 2

Digestion: Ingestion

Answer 2

taking in of food

Question 3

Digestion: Digestion

Answer 3

chemically + mechanically breaking down food

Question 4

Digestion: Absorption

Answer 4

taking the nutrients from the food

Question 5

Digestion: Elimination

Answer 5

release of waste into the environment

Question 6

Digestion

Answer 6

the process of breaking down tissues of another organism to make them available for absorption, and can be accomplished by an incomplete or complete DS

Question 7

Incomplete Digestive System

Answer 7

AKA gastrovascular cavity; feature a digestive cavity with a single opening that functions as both a mouth and anus
- ingested materials enters the mouth/anus + passes into a cavity lined with cells that secrete digestive enzymes
- food particles are absorbed by the cells lining the cavity
- once digestion is completed, the remaining materials are eliminated as waste through the mouth/anus
- seen in animals with radial symmetry (cnidaria)

Question 8

Complete Digestive System

Answer 8

AKA alimentary canal; features a separate opening for the mouth + anus, allowing for both unidirectional food movement + regional specialization along the digestive tract
- ingested material enters the mouth and proceeds to the digestion site, then nutrient absorption site, then is excreted through the anus
- present in nearly all bilaterally symmetrical animals (except flatworms)

Question 9

Digestive System Overview

Answer 9

• intake of food
• digestion of food into nutrients
• absorption of nutrients (circulatory system/directly into tissues)
• elimination of waste

Question 10

Mouth

Answer 10

site of ingestion; mechanical and/or chemical digestion may begin here

Question 11

Mouth: MECHANICAL

Answer 11

only begins in the mouth if the animal has teeth and a jaw structure adapted for chewing

Question 12

Mouth: CHEMICAL

Answer 12

begins in the mouth for a subset of nutrients only if the animal produces the appropriate digestive enzymes in their saliva

Question 13

Esophagus

Answer 13

transports swallowed food from the mouth to the next site in the digestive tract - either a crop, stomach, gizzard, or rumen

Question 14

Crop

Answer 14

food storage location prior to digestion
- present in some birds and many invertebrates

Question 15

Stomach

Answer 15

location for both mechanical + chemical digestion in most animals
- has powerful muscles that mechanically break down food as the stomach muscles contract
- produces digestive enzymes that break down food into their nutrients

Question 16

Gizzard

Answer 16

additional location for mechanical breakdown of food present in animals that lack teeth or have a jaw structure that does not allow for chewing
- EX: vertebrates (birds + reptiles) and many invertebrates

Question 17

Rumen

Answer 17

houses symbiotic bacteria and protists capable of digesting grass + cellulosic material
- found in hoofed herbivores called ruminants (cows, sheep, goats, grazing animals)

Question 18

Small Intestine

Answer 18

late site of chemical digestion + the location where nutrients are absorbed into the body
- food travels here after going through a crop, stomach, gizzard, and/or rumen
- chemical digestion is mediated by accessory organs like the liver + pancreas
- has massive SA to support nutrient absorption

Question 19

Cecum

Answer 19

located at the junction between the small and large intestines
- in herbivores, it houses symbiotic bacteria capable of digesting cellulose

Question 20

Large Intestine

Answer 20

FINAL location for food that has now been digested and nutrients absorbed; NOT INVOLVED IN DIGESTION but serves critical roles related to digestion:
- helps reabsorb a lot of water used in digestion
- colon reabsorbs salts used in digestion
- colon houses a lot of microbes that contribute to host health by synthesizing vitamins and excluding pathogenic bacteria

Question 21

Adaptation for Ingestion

Answer 21

• Invertebrate Mouth Parts
• Vertebrate Jaw Structure
• Teeth
• Crop

Question 22

ADAP: Invertebrate Mouth Parts

Answer 22

invertebrates lack teeth, but have a wide array of mouth structures adapted to different food
- bees have structures to facilitate nectar lapping
- grasshoppers have structures to chew vegetation
- butterflies have structures to siphon nectar

Question 23

ADAP: Vertebrate Jaw Structures

Answer 23

varies widely across species
- jaw flexibility

Question 24

ADAP: Teeth

Answer 24

different types of teeth are adapted to different foods
- Incisors work well for biting
- Canines work well for tearing food off a larger mass; larger in carnivores
- Molars work well for chewing; flatter and more numerous in herbivores and omnivores

Question 25

ADAP: Crop

Answer 25

adaptation that allows animals to eat in excess when food is abundant, then store food for later digestion

Question 26

Adaptations for Digestion

Answer 26

- Symbiotic Microorganisms - Cecum + Rumen - Gizzard

Question 27

ADAP: Symbiotic Microorganisms

Answer 27

the DT of all animals contain symbiotic microorganisms which perform their own food digestion within the animal - mutually beneficial; microorganisms have a steady supply of nutrients and are protected while the animal has access to nutrient byproducts produces by microorganisms - many vitamins and nutrients are inaccessible until released by the digestive activity of symbiotic bacteria in the gut

Question 28

ADAP: Cecum + Rumen

Answer 28

- digestion of plant material required addition steps; some can only be done by microorganisms - herbivores have adaptations to support specific bacteria within their DY, where they ferment plant fibers and material to release once unavailable nutrients

Question 29

ADAP: Large Cecum

Answer 29

present in ruminant herbivores; pouch-like structure at the junction of the small + large intestines that house symbiotic bacteria capable of digesting cellulose - the appendix is the vestigial cecum in humans

Question 30

ADAP: Rumen

Answer 30

present in ruminant herbivores; a fermentation vat of symbiotic bacteria + protists to digest cellulose - anaerobic environment - this and accessory organs (reticulum, omasum, abomasum) are present in ruminant and grazing animals

Question 31

ADAP: Gizzard

Answer 31

in both invertebrates and vertebrates that lack teeth entirely (birds) or teeth/jaw supported chewing (reptiles) - used as a more mechanical breakdown of food - can break down food, sand, or grit to facilitate digestion

Question 32

Enzymes in Digestion

Answer 32

- Amylase - Bile Salts - Lipase - Nuclease - Pepsin - Trypsin/Chymotrypsin

Question 33

Amylase

Answer 33

- breaks down starches - produces and active in the mouth and pancreas - salivary amylase is not present in obligate carnivores

Question 34

Bile Salts

Answer 34

- breaks down lipids via emulsification - produced in the liver - stored in the gallbladder - active in the small intestine - facilitate emulsification rather than true chemical breakdown

Question 35

Lipase

Answer 35

- breaks down lipids - produced in the mouth, stomach, and pancreas - active in the mouth, stomach, and SI - the bulk of lipid digestion occurs in the SI due to pancreatic lipase

Question 36

Nuclease

Answer 36

- breaks down nucleic acids - produced by the pancreas - active in the SI

Question 37

Pepsin

Answer 37

- breaks down protein - produced and active in the stomach - secreted in an inactive form to be activated by the low pH of stomach acid

Question 38

Trypsin/Chymotrypsin

Answer 38

- breaks down proteins - produced by the pancreas - active in the SI

Question 39

Digestive Process: STEP ONE

Answer 39

begins when food enters the mouth/oral cavity; both mechanical and chemical digestion occur - the teeth grind and break up food, supported by the tongue - salivary amylase breaks down carbohydrates - lingual lipase breaks down fats

Question 40

Digestive Process: STEP TWO

Answer 40

after it is swallowed, the chewed food (called bolus) moves down the esophagus, taking the bolus to the stomach - NO digestion occurs here

Question 41

Digestive Process: STEP THREE

Answer 41

the bolus reaches the stomach, where both mechanical and chemical digestion occur over multiple hours - the muscles of the stomach walls churn the bolus, mixing it with gastric acids (gastric lipase + pepsin) - the stomach is lined with a layer of protective mucus, insulating the cells from direct contact with gastric acid + enzymes - converts bolus into CHYME

Question 42

Digestive Process: STEP FOUR

Answer 42

the chyme is transported into the small intestine where the majority of chemical digestion occurs - NO mechanical breakdown occurs here - the SI does not produce any digestive enzymes, but relies on accessory organs

Question 43

STEP FOUR Expanded

Answer 43

- the pancreas releases pancreatic amylase, nuclease, trypsin, and pancreatic lipase - bile salts are released to digest fats by promoting emulsification

Question 44

Emulsification

Answer 44

the breakdown of larger lipid "globules" into smaller globules more widely distributed in the chyme, creating more SA on fat molecules to facilitate digestion and absorption

Question 45

Nutrient Absoprtion

Answer 45

occurs in the SMALL INTESTINE - lining is highly folded, each fold has multiple villi and microvilli to increase SA - close to the surface of each villus is a network of blood vessels and lymphatic vessels, which minimize the distance required for absorption

Question 46

Absorption of: Sugars + AA

Answer 46

absorbed into the villi + then into the blood vessels absorb this via facilitated diffusion or cotransport (depending on the nutrient)

Question 47

Absorption of: Lipids

Answer 47

not soluble in aqueous environments; the digested fats from sphere called micells, which diffuse into and coated in proteins to form larger spheres called chylomicrons - chylomicrons contain a mix of digestive lipids and are transported from the villi into the lymphatic system via exocytosis