1. Basic Principles of Animal Form & Function
Chapter 40
Basic Principles of Animal Form & Function

2. Anatomy & Physiology
anatomy – the study of the structure of an organism
physiology – the study of the functions an organism performs
natural selection can fit structure to function by selecting, over many generations, what works best among the available variations in a population

3. relationship between structure & environment

4. Exchange with the Environment
an animal’s body plan must allow all of its living cells to be bathed in an aqueous medium to main the fluid integrity of the plasma membrane
this is easy for…
a single-celled organism (ie: protist) because its entire surface area is in contact with water
a simple animal (ie: a hydra or flatworm) that has a 2-layered sac or flat body plan that puts a large surface area in contact with the environment

6. continued…
complex animals require extensively folded or branched internal surfaces to facilitate exchange with the environment

7. levels of organization in animals
form & function are correlated at all levels of organization

8. Tissues
tissues are groups of cells with a common structure and function
different types of tissues have different structures that are suited to their function
4 main types of tissues:
epithelial
connective
muscle
nervous

9. Epithelial Tissue
covers the outside of the body and lines organs & cavities within the body
sheets of tightly packed cells
enables the epithelium to function as a barrier against mechanical injury, microbes, & fluid loss
criteria for classifying epithelial tissue:
# of cell layers: simple (single layer) or stratified (multiple layers)
shape of cells: cuboidal (like dice), columnar (like bricks standing on end), or squamous (like floor tiles)

10. Connective Tissue functions mainly to bind & support other tissues
consists of a sparse population of cells scattered through an extracellular matrix
3 kinds of connective tissue fibers:
collagenous – made of collagen; nonelastic & do not tear easily when pulled lengthwise
elastic – made of elastin; provide a rubbery quality that complements the nonelastic strength of collagenous fibers
reticular – made of collagen; thin & branched; continuous with collagenous fibers; form a tightly woven fabric that joins connective tissue to adjacent tissue

11. continued… major types of connective tissue:
loose connective tissue
adipose tissue
fibrous connective tissue
cartilage
bone
blood
2 predominant types of cells in loose connective tissue:
fibroblasts – secrete protein ingredients of the extracellular fibers
macrophages – amoeboid cells that roam the maze of fibers, engulfing foreign particles & the debris of dead cells by phagocytosis
continued…

12. Muscle Tissue
composed of long cells called muscle fibers that are capable of contracting
arranged in parallel within the cytoplasm of muscle fibers are large numbers of contracting units called myofibrils made of the proteins actin and myosin
most abundant tissue in most animals
muscle contractions account for much of the energy-consuming cellular work in an active animal
3 types: skeletal, cardiac, & smooth

13. Nervous Tissue
senses stimuli & transmits signals in the form of nerve impulses from one part of the animal to another
functional unit = neuron
concentrated in brain

14. Organs & Organ Systems tissues are organized into organs
many of the organs of vertebrates are suspended by sheets of connective tissue called mesenteries
mammals have two body cavities separated by a sheet of muscle called the diaphragm:
thoracic cavity – houses lungs & heart
abdominal cavity – most other organs
organs work together in organ systems to carry out the major body functions of most animals

15. 11 Organ Systems

16. bioenergetics
the flow of energy through an animal

17. Energy & Allocation animals harvest energy from the food they eat
food is digested by enzymatic hydrolysis & energy-containing molecules are absorbed by body cells
most of these molecules are used to generate ATP
after energetic needs are met, any remaining molecules from food can be used in biosynthesis (body growth & repair, synthesis of storage materials such as fat, and gamete production)

18. Quantifying Energy Use
metabolic rate = amount of energy an animal uses in a unit of time
can be measured by:
monitoring an animal’s rate of heat loss
determining the amount of O2 consumption or CO2 production by cellular respiration
estimating the rate of food consumption & the energy content of the food consumed
energy is measured in calories (cal) or kilocalories (kcal)
metabolic rate is closely related to an animal’s bioenergetic strategy: endothermic or ectothermic
in general, endotherms have higher metabolic rates than ecototherms

19. Influences on Metabolic Rate
size
it’s been shown that the amount of energy it takes to maintain each gram of body weight is inversely related to body size (explanation is still unclear)
activity
minimum rate powers the basic functions that support life
endotherms  basal metabolic rate (BMR)
non-growing, resting, fasting, non-stressed
ectotherms  standard metabolic rate (SMR)
resting, fasting, a particular temperature
maximum rate is inversely related to the duration of activity
many factors influence metabolic rate between these extremes: age, sex, size, body & environmental temperatures, quality & quantity of food, activity level, oxygen availability, hormone balance, and time of day

20. Energy Budgets
different animals use the energy and materials in food in different ways, depending on:
environment
behavior
size
basic strategy of endothermy or ectothermy

21. homeostasis (internal balance)

22. Coping with Environmental Fluctuations
regulators – animals that use internal control mechanisms to moderate internal change in the face of external fluctuation
conformers – animals that allow their internal condition to vary with certain external changes
no organism is a perfect regulator or conformer

23. Mechanisms of Homeostasis
3 functional components of a homeostatic control system:
receptor – detects a change in some variable of the animal’s internal environment
control center – processes info it receives from receptor & sends appropriate response to effector
effector - initiates response to reverse the change
control circuits exhibit negative feedback:
change triggers the control mechanism to counteract further change in the same direction, which prevents small changes from becoming too large
a large portion of the energy from food is used to maintain homeostasis

24. example of negative feedback

25. thermoregulation
the process by which animals maintain an internal temperature within a tolerable range

26. Ectotherms common misconception:
ectotherm means an animal has variable body temperature & are “cold-blooded” (ie: have low body temperatures)
ectotherms are animals that use heat from the environment as the source of heat for maintaining body temperature

27. Endotherms common misconception:
endotherm means an animal has constant body temperature & are “warm-blooded”
endotherms are animals that use metabolic heat to regulate their body temperature
advantages of endothermy:
enables animals to perform vigorous activity for longer periods of time
enables animals to maintain stable body temperature on land where temperature fluctuations are generally more severe
disadvantages:
cannot tolerate large fluctuations in internal temperatures like ectotherms
energetically expensive

28. Modes of Heat Exchange 4 processes:
conduction – transfer of heat between 2 objects in direct contact
convection – transfer of heat by the movement of air or liquid past a surface
radiation
evaporation
heat is always transferred from an object of higher temperature to one of lower temperature

29. Adaptations for Thermoregulation
insulation
reduces the flow of energy between an animal & its environment and lowers the energy cost of keeping warm
hair, feathers, fat layers (ie: adipose tissue)
raising fur or feathers traps a thicker layer of air, reducing heat loss
circulatory adaptations
vasodilation – increase in diameter of superficial blood vessels; helps release heat by radiation, conduction, & convection
vasoconstriction – decrease in diameter of superficial blood vessels; reduces heat loss
countercurrent heat exchanger
traps heat in the body core to reduce heat loss by direct transfer of heat in arterial blood to venous blood

31. continued… evaporative heat loss behavioral responses
loss of water by evaporation across skin & via breathing cools the body because the water absorbs a considerable amount of heat when it evaporates
adaptations that promote evaporative heat loss include panting & sweating
behavioral responses
simple behaviors like moving between sun & shade
more complex behaviors like hibernation & migration
adjusting metabolic heat production
shivering
nonshivering thermogenesis (NST)
hormones cause mitochondria to increase their metabolic activity and produce heat instead of ATP
in some mammals, a tissue called brown fat in the neck & between the shoulders is specialized for NST
continued…

32. Feedback Mechanisms in Thermoregulation
nerve cells that control thermoregulation are concentrated in the region of the brain called the hypothalamus
responds to changes in body temperature above or below the normal range by activating mechanisms that promote heat loss or gain
functions as a thermostat
warm receptors signal hypothalamus when temperature increases
cold receptors signal hypothalamus when temperature decreases

33. Adjusting to Changing Temps.
acclimatization – adjustment to a new range of environmental temperatures over a period of days or weeks
in endotherms, may include adjusting amount of insulation
in ectotherms, often includes adjustments at the cellular level such as increasing the production of certain enzymes or producing enzyme variants that have the same function but different optimal temperatures

34. Torpor
torpor = a physiological state in which activity is low & metabolism decreases
enables animals to save energy while avoiding difficult or dangerous conditions
3 examples:
hibernation = long-term torpor that is an adaptation to winter cold & food scarcity
estivation = summer torpor that enables animals to survive long term periods of high temperatures and scare water supplies
daily torpor – exhibited by small mammals & birds; based on feeding patterns