Animal size and homeostasis

Question 1

Why are the smallest and the largest animals aquatic?

Answer 1

Largest invertebrates and mammals are larger in water than on land.
Smallest mammals and reptiles are larger in water than on land.

Largest reptiles are aquatic e.g aquatic crocodile vs terrestrial komodo dragon

Question 1

How does the size influence an organism?

Answer 1

Influences the evolution.
Aquatic animals (vertebrates) tend to be larger.

Question 2

What is this pattern driven by?

Answer 2

many biochemical and physiological processes need the transfer of materials and energy between the exterioir and interiro of the organism.

Question 3

Adaptability depends on the enviornment?

Answer 3

Size influences the exchange or uptake of O2, CO2, Water, food and heat.

Question 4

Do larger animals or smaller animals have a higher SA:V?

Answer 4

Smaller organisms have a larger SA:V than larger animals of the same shape.

But some larger mammals have adaptions for higher SA:V e.g. elephant has folded skin to increase the SA:V.

Question 5

How does the size of an organisms influence gaseous exchange?

Answer 5

Need O2 for respiration and releases CO2 as a waste product.
- O2 readily diffuses into cells and crosses (1mm of tissue in sec & 21mm in 1hr) - takes to long for larger animals, therefore aniamals adapted.

Question 6

How do animals deal with effective gaseous exchange?

Answer 6

1. Changing shape
2. Active transport of oxygen into the interior of the body

Question 7

How does shape change influence gaseous exchange?

Answer 7

increase the surface area (either flattening / outgrowths)

flattening decreases the distance that gasses need to travel to get to important organs.

Question 8

How does Active transport of oxygen into the interior of the body influence gas exchange?

Answer 8

Tubular body with central chamber - water drawn into the inner chamber
allows oxygen to diffuse to interior cells.
Organs and organ systems that bring O2 into the body and transport it around the body - Circulatory system AND lungs/gills.

Question 9

What are adaptions to maximise O2 uptake?

Answer 9

depends on the environment.
▪ O2 concentration is higher in terrestrial than aquatic environments.

In aquatic environments:
▪ oxygen may be taken directly from the water (fish, amphibians, invertebrates) or from the atmosphere (mammals, birds, some fish & amphibians)
▪ Anoxic (i.e., no oxygen) conditions can occur

Question 10

How do Different nutritional needs and ways of
acquiring energy and nutrients?

Answer 10

Size & complexity of an animal influences acquisition of energy and nutrients (food) and the release of waste products from digestion.

Small, simple aquatic (marine) animals
▪ Absorb dissolved nutrients across body surface - Sponges, Larvae.

Larger, more complex animals need a digestive system.
▪ a tube in which digestion occurs
▪ Complexity of digestive system depends on diet

Where nutrients across the skin the organisms is limited in size - cannot apply to terrestrial animals.

Question 11

What is a herbivore?

Answer 11

Only feed on plants often have long complex digestive structures.

Question 12

What are problems associated with being a herbivore?

Answer 12

▪ Low in proteins / nitrogen
▪ High in structural carbohydrates that need to be converted to animal tissue to be assimilated - therefore animals have enteric gut flora (gut bacteria/protists to break down cellulose/lignin).

Question 13

How can animals adapt to the problems?

Answer 13

Quality of food important for herbivores
▪ Need high nitrogen food
▪ increases growth, reproductive success, survival of animals
▪ N content influences what animals eat & when they reproduce

Question 14

What is a carnivore?

Answer 14

Eat other animals have relatively simple digestive systems.
Quantity in NB

Question 15

What are the problems with carnivory?

Answer 15

Do not have problems
▪ with food quality or digesting cellulose
▪ digesting and assimilating nutrients from prey
▪ chemical composition of the tissues is similar to own

Question 16

What is an omnivore?

Answer 16

eat plants and animals
▪ Diet can vary with the seasons, stages in the life
cycle, size, and growth rate
▪ red foxes eat berries and grasses, some insects and
small rodents
▪ black bears eat mainly vegetation, including buds, nuts, tree bark, and supplement with insects, fish, and small to medium mammals
▪ frogs usually eat algae as tadpoles and insects as
adults

Question 17

How can animals Respond to Variations in the External Environment?

Answer 17

▪ Conformers have an internal environment ~ that of the external environment
▪ Regulators regulate internal conditions relative to the external environment

Question 18

How do Animals exchange heat/energy with their surrounding environment?

Answer 18

Animals may produce heat internally AND / OR absorb heat from surroundings - maintian optimal temp for metabolic processes, lose excess heat - depends on where they live.

Terrestrial & aquatic animals face different
challenges to maintaining an optimal Tb - Terrestrial environemtns are more variable than aquatic environments.

Animals can regulate body temperature through
behaviour, physiology and morphology

Question 19

What are the factors influencing rate of heat loss & gain?

Answer 19

Body size
body shape
Heat gain affects dessication in terrestrial species.

Question 20

How does body size influence the rate of heat loss/gain?

Answer 20

Smaller animals lose or gain heat faster than larger ones.

Question 21

How does body shape influence the rate of heat loss/gain?

Answer 21

Projections on body surface will increase loss or gain of heat.
Changing area absorbing heat influences eat gain.

Question 22

Limpet example

Answer 22

Change shape as they grow - become taller
- ridges and bumps increases the surface across which they are reflecting heat.
- absorbing less heat due to smaller size

Question 23

Gastropod example

Answer 23

Hide away more and are under rocks to prevent being washed away.

Question 24

Poikilotherms

Answer 24

▪ Have a variable body temperature
▪ regulate body temperature through exchange of heat
with surrounding environment
▪ Ectothermy
▪ Invertebrates, amphibians, reptiles & fish

Question 25

Homeotherms

Answer 25

▪ Have a constant, or nearly constant, body
temperature
▪ Generate metabolic heat internally to regulate body
temperature
▪ Endothermy
▪ Mammals & birds

Question 26

For poikilotherms body temperature can have
serious implications for performance

Answer 26

▪ Low metabolic rate
▪ Gain & lose heat easily
▪ Limits physical activity
▪ Relative performance changes with
body temperature
▪ Each species has Tmin,
Tmax and Topt

Question 27

Temperature tolerances of Poikilotherms usually
depends on temperature of habitat

Answer 27

▪ Tmin, Tmax & Topt correlated to
temperature of the habitat of a
species
▪ Aquatic poikilotherms are poorly
insulated
▪ Maintaining a body temperature
much different to that of the
water temperature very difficult