The Basics of Animal Form and Function

Ch. 33

Objective

Content: Describe how living things use free energy to

maintain homeostasisSkill: Connect and relate knowledge across domains

Life exists in all parts of the

world Animals inhabit every part

of the Earth Amazing diversity of

habitat, form, and function Natural selection favors

individuals who can meet the demands of their particular environment

Physical Laws & the Environment Constrain Animal Size & Shape

Flying animals can only get so big… Physics of flight would never

allow a flying dragon Water is 1000x more dense

than air Any bump on the body causes

drag Fast swimmers all have

torpedo shaped bodies An example of convergent

evolution

Another example is single-celled organisms Surface area to volume ratio is important

Keeps single celled organisms very small and flat

In multicellular animals: all the cells must have access to an aqueous

environment branching and folding of internal parts help

accomplish this

Example 1: Microvilli in intestinal cells

Example 2: Root hairs in plants

Example 3: branching and folding of cell membrane in amoeba

Example 4: long flat body of a tapeworm

Example 5: flat body of Platyhelminthes

Quick Think How does a large surface area contribute to

the functioning of the small intestine? How does a large surface area of organs

benefit larger organisms like blue whales and humans?

Levels of Organization in

complex animals

Cells - smallest functional unit Tissues - groups of cells with a common structure and

function 4 types of tissue:

1. Epithelial - sheets of tightly packed cells; covers the body and lines the organs

2. Connective tissue - supports & binds other tissues; made up of scattered cells in the ECM; examples - cartilage, tendons, ligaments; bone; blood

3. Nervous tissue - made up of neurons; senses & transmits info4. Muscle tissue - made up of long cells called muscle fibers; can contract

when stimulated; 3 types: cardiac, skeletal, smooth

Organs - organized groups of tissues

Organ systems - groups of organs that work for a common purpose Example: digestive

system

Animals use the chemical energy in food to maintain homeostasis, grow, & reproduce

Metabolic rate - the amount of energy an animal uses in a given amount of time Energy measured in calories or

kcal 2 basic “strategies”

Endotherms - animals bodies warmed by heat generated through metabolism

Ectotherms - animals bodies warmed by environment - metabolism does not produce enough heat to warm the body

Lizard sunning itself on a rock to warm up

Endotherms Birds and mammals Body temp maintained by

metabolism Much energy required Permits intense, long

duration activity In general, the smaller the

endotherm, the higher the metabolic rate

Ectotherms Fish, amphibians, reptiles,

invertebrates Body temp controlled by

environment Less energy required Move more slowly when cold

Quick Think

If a mouse and a small lizard of the same mass were placed in a respirometer under identical environmental conditions, which animal would consume oxygen at a higher rate? Explain.

Maintaining a constant internal environment

Homeostasis - the state of internal balance 2 main strategies:

Regulator - some animals are this type - they moderate internal change in the face of external fluctuations (keeping body temp constant by sweating, shivering)

Conformer - some animals are this type - allow their internal conditions to vary with the environment

These are the 2 extremes - most animals use some of both

Regulator or Conformer? - Can drop it’s body temp 50 degrees at night to deal with freezing overnight conditions

Mammals are endotherms - use metabolism to adjust for fluctuations in environment

Fish & aquatic inverts. are conformers - they live in stable environments and can adjust bodies for slight changes in environment

Modes of heat exchange

Conduction - the transfer of heat between objects in direct contact with each other Example - animal sitting in

cool water Convection - transfer of heat

through the movement of air or liquid past a surface Example - a cool breeze

Radiation - the emission of electromagnetic waves by warm objects(anything warmer than absolute zero)

Evaporation - removal of heat from the surface of a liquid as molecules leave the surface as gas Example - as sweat evaporates off

skin it cools the skin

Thermoregulation How animals maintain their internal temperature Takes place through the following processes:

1. Adjustment of the rate of heat exchange between the animal and its environment through hair, feathers, fats - is accomplished through: 1. vasodilation (blood vessels expand near skin, cools the blood)2. vasoconstriction (blood vessels contract away from skin, keeps blood

warm)

2. Evaporation across the skin (panting or sweating)

3. Behavioral responses like changing location or body position

4. Alteration in the rate of metabolic heat production in endotherms

2. 3.

Mechanisms of Homeostasis Negative feedback - a change

in one variable (the output) triggers a change in the control center which turns the system off Example - human body

temperature Positive feedback - a change

in one variable (the output) triggers the control center to amplify the output Example - nursing by babies

(the more the baby nurses, the more milk is produced by the mother)

Quick Think Describe the difference between positive

and negative feedback mechanisms. Which one is more common in living

things?

Energy Budgets For most animals – the majority of food

energy goes to making ATP Very little goes toward growth or reproduction There is great variety in how animals “spend”

their energy budget

Reproduction and the rearing of offspring are “expensive”

These activities require extra energy Animals use different strategies depending

on energy availability Seasonal reproduction when food is available

Quick Think

Can ectotherms have stable body temperatures? Explain.

So in summary…

What did you learn today about the main mechanisms for how living things use free energy to maintain homeostasis?

Animal Nutrition

4 main feeding mechanisms Suspension feeders: sift small food

particles from water - ex: humpback whales, clams

Substrate feeders: live on or in their food source - ex: maggots, many insect larvae

Fluid feeders: take nutrient rich fluid from a living host - ex: mosquitos

Bulk feeders: eat relatively large pieces of food - ex: humans, most animals

Homeostatic mechanisms manage an animal’s energy budget

Example: glucose regulation Animals store excess calories

as glycogen in the liver & muscles & as fat

Animal can tap into these energy stores when it needs ATP

Blood glucose levels maintained within a narrow range by negative feedback Fat cells

Diet must supply carbon skeletons & essential nutrients

Essential nutrients - must be obtained in preassembled organic form because animal cannot produce them About 1/2 of the amino acids

needed for protein synthesis are essential amino acids - must be taken in through food

Vitamins (B, E, C (in humans, birds, snakes))

Minerals (Ca, P)

Caribou eating shed antlers to get needed phosphorus

Processing Food 4 main stages:

Ingestion - taking food in

Digestion - breaking down food into small molecules that cells can absorb (by enzymatic hydrolysis)

Absorption - body cells take up nutrients from digestive tract

Elimination - undigested material passes out of digestive tract

2 main types of digestion Intracellular - occurs within cells

enclosed by a protective membrane - sponges do this

Extracellular - food is broken down outside of cells - most animals do this

Simple animals have a gastrovascular cavity for digestion with a single opening for food & waste

Complex animals have complete digestive tracts (alimentary canals), one way flow, 2 openings

One way flow

The organs of the mammalian digestive system

Mouth - food in the mouth triggers the secretion of saliva Saliva lubricates the food to aid

in swallowing Saliva contains amylase -

breaks down carbs Chewed food called a bolus Swallowed food enters the

pharynx - tube that opens into esophagus & trachea Epiglottis (flap of cartilage)

covers the opening to the trachea so food goes down the esophagus

Esophagus - uses peristalsis (wave like contractions) to move food to stomach

Stomach - stores food, secretes very acidic (pH 2) gastric juices Juices break down the ECM of

meat and plants; kills most bacteria

Pepsin -enzyme in gastric juices; secreted as pepsinogen (inactive form) then activated by HCl

Result of stomach digestion is a substance called acid chyme This is moved into the

small intestine via the pyloric sphincter

Small intestine - first section called duodenum Here the acid chyme mixed with secretions from

pancreas, gallbladder Rest of small intestine responsible for absorbing nutrients Lining of small intestine has lots of little folds called villi

Villi has folds called microvilli These greatly increase SA for absorption

Large intestine - AKA colon Connected to small intestine by

a sphincter where the cecum is found Cecum is a small pouch with the

appendix Main function of colon is to

absorb water & compact waste Colon ends at rectum - feces

stored here until eliminated

Dentition We can tell what

an organism eats based on its teeth (dentition)

Herbivores usually have longer digestive tracts - since vegetation takes longer to digest