Post on 15-Apr-2017
transcript
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