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Animal Form/Function/Nutrition (Thermoregulation (Balancing Heat Loss and…
Animal Form/Function/Nutrition
Form and Function Correlation
Size and Shape
Physical laws that govern strength, diffusion, movement, and heat exchange limit the range of animal forms
Physical laws also influence animal body plans with regard to max size
As body dimensions increase, thicker skeletons are required to maintain adequate support
As bodies increase in size, the muscles required for movement have to represent even larger fractions of body mass
Animal size and shape greatly affect how it interacts with its environment
Exchange with environment
Animals have to exchange nutrients, waste products, and gases with their environments
Exchange occurs as substances dissolved in an aqueous solution move across the plasma membrane of each cell (diffusion)
The rate of exchange is proportional to membrane surface area involved in exchange
the amount of material that must be exchanged is proportional to the body volume
In most animals, specialized features that are extensively branched or folded enable adequate exchange with the environment
These features almost always lie inside the body protecting delicate tissues
Branching/folding increases surface area, allowing sufficient exchange
Internal body fluids link exchange surfaces to body cells (
interstitial fluid
)
Complex body plans also have a circulatory fluid (like blood)
Having both fluids in a body plan ensures that cells are able to obtain the nutrients they need and get rid of any waste
Complex bodies have distinct benefits over simple ones (internal digestion, sensory organs)
Complex body plans especially favor land animals, as the external environment is extremely volatile
Hierarchical Org of Body Plans
Cells --> Tissues --> Organs --> Organ System
Organs have tissues with distinct physiological roles, sometimes different enough for an organ belong to multiple organ systems
The specialized and complex organ systems of animals are built from a limited set of cell and tissue types (I.e. lungs and blood function differently but vessels are lined by same type of tissue)
Four main types of animal tissues
Epithelial
Covers the outside of the body and lines organs/cavities within the body
closely packed with tight junctions, functioning as a barrier against mechanical injury, pathogens, and fluid loss
Connective
Sparse population of cells scattered through an extracellular matrix, holding many tissues/organs together
Matrix usually consists of web fibers embedded in a liquid, jellylike, or solid foundation
3 types:
Collagenous
fibers provide strength and flexibility
Reticular fibers join connective tissue to adjacent tissues
Elastic fibers make tissue elastic
Fibroblasts
(secrete fiber proteins) and macrophages (engulf foreign particles and any cell debris by phagocytosis) are both found in the matrix
Muscle
The tissue responsible for nearly all types of body movement
all muscle cells consist of filaments containing the proteins actin and myosin (together make muscles contract)
3 kind:
skeletal muscles are responsible for voluntary movements
smooth muscle are responsible for involuntary body activities
Cardiac muscles form the contractile wall of the heart; has fibers that relay signals from cell to cell to synchronize heart contraction
Nervous
Functions in the receipt, processing, and transmission of information
Nervous tissue contains neurons (nerve cells) that transmit new impulses, as well as support of glial cells (which support neurons)
Coordination and Control
Endocrine System
Signaling molecules released into the bloodstream by endocrine cells are carried throughout the body
Signaling molecules sent throughout the body are called
hormones
Different hormone=distinct effects
Only cells that have receptors for a particular hormone respond
Hormone may only have effect in single location depending on cell receptor
Hormones can be released in seconds and stay in body for hours
Nervous System
Neurons transmit signals alone specific routes connecting specific locations in the body
Nerve impulses
travel to specific target cells along communication lines consisting of mainly axons
Nerve impulses can act on other neurons, muscle cells, cells and glands that produce secretions
Unlike the endo. system, the nervous system conveys information by the
pathway
each signal takes
Ex: A person can notice different musical notes because each note's frequency activates different neurons
Communication usually involves more than one type of signal
Nerve impulses take only a fraction of a second to reach target and only last for a fraction of a second
Different signal type/transmission/speed/duration = Different function
Nervous
Directing immediate and rapid responses to the . enviornment
Ex. reflexes, "knee-jerk reactions," or other rapid movements
Endocrine
Gradual changes that affect entire body
Ex. growth, development, reproduction, metabolic processes, and digestion
Feedback Control
Regulating and Conforming
Regulator
- Animal that uses internal mechanisms to control internal change in the face of external change
(Ex. Otters self-regulate body temp)
Conformer
- Animal that allows its internal condition to change based on external changes
(Ex. Bass body temp usually matches that of the water it's in)
An animal may regulate some internal conditions while other conditions can conform to outside environment
Homeostasis
Steady state; maintenance of internal balance
Animals maintain a relatively constant internal environment even during drastic external changes
Can be exhibited in a range of physical/chemical properties
(Ex. Humans generally maintain body temp of 98.6, blood pH within .1 pH unit of 7.4, and blood glucose concentration at 70-110 mg per 100 mL of blood)
Mechanisms of Homeostasis
Set Point
- particular value needed to reach homeostasis
Stimulus
- Fluctuation in the variable above/below the set point
Sensor
- Detects stimuli; Sends signal to control center
Control Center
- Receives signal from sensor, generates output to trigger response
Response
- Physiological activity that helps return the variable to the set point
Feedback Control in Homeostasis
Negative Feedback
- Control mechanism that reduces the stimulus
(Ex. Sweating until body is cooled down, then stop sweating)
Homeostasis in animals relies largely on negative feedback
Homeostasis is an intermingling relationship between external factors changing internal environments and internal control mechanisms that fight those changes
Physiological responses to stimuli are not instantaneous. As a result,
homeostasis moderates but does not eliminate changes in the internal environment
Additional fluctuation occurs if a variable has a
normal range
(upper and lower limit)
Positive Feedback
- Control mechanism that amplifies rather than reduces the stimulus
In animals, positive feedback does not play a large role in homeostasis
Instead it helps drove processes to completion (Ex. Childbirth - pressure of baby's head stimulates uterus to contract)
Alterations in Homeostasis
Regulated Changes
in the internal environment are essential to normal body functions
Some occur at particular stages in life (radical change in hormone balance during puberty) or cyclically (women's menstrual cycle)
Certain cyclic alterations in metabolism reflect a
circadian rhythm
(set of physiological changes that occur roughly every 24 hours)
Circadian rhythms are elemental to the body, even though the biological clock is usually coordinated with the cycle of light/dark
Acclimatization
- Gradual process by which an animal adjusts to changes in its external environment
Do not confuse acclimatization (a temporary change) with adaptation
Thermoregulation
Thermoregulation
- Process by which animals maintain their body temperature within a normal range
Body temps outside normal ranges can reduce the efficiency of enzymatic reactions, change fluidity of cellular membranes, and (fatally) affect more temp-sensitive biochemical processes
Endothermy and Ectothermy
Endothermic
Animals warmed mostly by metabolism generated heat
Endotherms can maintain a stable body temp even during large changes in environmental temp
In cold environments endotherms generate enough body heat to stay warmer than its surroundings
In hot environments, some endotherms have mechanisms for cooling their bodies, enabling them to withstand heats ectotherms can't
Ectothermic
Animals that gain most of their heat from external sources
Many ectotherms adjust their body temp by behavioral means, such as seeking out shade or basking in the sun
Bc their heat source is mostly environmental, ectotherms usually eat a lot less food than endotherms of equivalent size
Ectotherms usually tolerate larger fluctuations in their internal temp
They are not mutually exclusive (Endotherms can use the sun to warm up)
Variation in Body Temperature
Poikilotherm
- Animal whose body temp varies with its environment
Homeotherm
- has a relatively constant body temp
Several mechanisms mammals use to reduce/favor heat exchange involve the
integumentary system
(outer covering of the body, consisting of the skin, hair, and nails)
Balancing Heat Loss and Gain
Insulation
Many animals that rely on insulation to reduce overall heat exchange adjust their insulating layers to help thermoregulate
Insulation is extremely important for marine mammals (whales and walruses)
Transfer of heat to water occurs 50-100 times quicker than heat transfer to air
Reduces the flow of heat between animal's body and the environment
Behavioral Responses
BOTH
endotherms and ectotherms control body temp through behavioral responses to changes in the environment
Ectotherms maintain a nearly constant body temp by engaging in pretty simple behaviors
When cold, they seek warm places, orienting towards heat
When hot, they bathe, move to cool areas, or turn away from the heat source
Circulatory Adaptations
Provide a major route for heat flow between interior/exterior of the body
Vasodilation
- widening of superficial blood vessels (near the body surface)
increase in vessel diameter leads to increase in blood flow in the skin
Vasoconstriction
- Reduces blood flow and heat transfer by decreasing the diameter of superficial vessels
Like endotherms, some ectotherms control heat exchange by regulating blood flow
Countercurrent Exchange
- the transfer of heat between fluids that are going in opposite directions
As warm blood moves from the body core to the arteries, heat is transferred to the colder blood returning from extremities
Cooling by Evaporative Heat Loss
In most situations, evaporation is the only way for animals to keep their body temp from rising
Water absorbs considerable heat when it evaporates
Some adaptations greatly facilitate evaporative cooling (bathing/sweating)
Many terrestrial mammals have sweat glands controlled by the nervous system
Adjusting Metabolic Heat Producttion
Due to endotherms having a higher body temp than the environment, they have to counteract continual heat loss
Thermogenesis
- varying of heat production to match changing rates of heat loss
Thermogenesis is increased by muscle activity (moving or shivering)
Non-shivering thermogenesis
Certain hormones cause mitochondria to increase their metabolic activity and produce heat instead of ATP
Brown Fat
- Tissue in some mammal's neck and shoulders specialized for rapid heat production
Together, non-shivering and shivering thermogenesis enables mammals/birds to increase metabolic heat production
Acclimatization in Thermoregulation among endotherms includes adjusting insulation (growing thicker/thinner coat of fur)
Acclimatization in ectotherms often includes cellular adjustments
Cells can produce variants of enzymes that have the same function but at different optimal temps
Sensors for thermoregulation happen in the
hypothalamus
Energy Requirements/Animal's Diet
Energy Requirements in Relation to Size
Energy Allocation/Use
Orgs can be classified by how they obtain chemical energy
Autotrophs harness light energy to build energy-rich organic molecules that they use for fuel
Heterotrophs get their chemical energy from food (which contains organic molecules synthesized by other organisms)
Most nutrient molecules are use to make ATP (produced by cellular respiration)
ATP powers cellular work, enabling cells, organs, and organ systems to perform necessary functions
ATP is also used for biosynthesis (needed for body growth and repair), synthesis of storage material (fat), and gamete production
Energy Use Quantified
Metabolic Rate
- sum of all the energy an animal uses in a given time interval
Energy is measured in joules, or calories and kilocalories (1kcal = 1,000 calories or 4,184 joules)
Metabolic rate can be measured by monitoring an animal's rate of heat loss
Can also be measured using the amount of oxygen consumed or carbon dioxide produced
Influences on Metabolic Rate
Size and Metabolic Rate
Larger animals need more chemical energy due to larger size
Metabolic rate remains roughly proportional to body mass to the three-quarter power (m^3/4)
The energy needed to maintain each gram of body mass is inversely related to body size
(a gram of a mouse needs around 20x as many calories as a gram of an elephant)
Torpor and Energy Conservation
Torpor
. - physiological state of decreased activity and metabolism enabling animals to save energy/avoid difficult situations
Hibernation
- long-term torpor that is an adaptation to . winter cold/food scarcity
Body temp declines as body's thermostat is turned down
Periodical arousal where mammals raise body temp/become active briefly
Metabolic rates during hibernation can be 20 times lower than normal
Animal's Diet Supplement
An adequate diet must satisfy three nutritional needs:
chemical energy for cellular processes
organic building blocks for macromolecules
Essential nutrients
Essential Nutrients
Essential nutrients are preassembled organic molecules and minerals
Essential Amino Acids
Animals require 20 amino acids to make proteins, half of which can be synthesized enzymatically (with sulfur and organic nitrogen in diet)
Remaining amino acids have to be gained through food in prefabricated form--known as essential amino acids
Amino acids most animals need
Isoleucine
leucine
lysine
methionine
phenylalanine
threonine
tryptophan
valine
Histidine (infants only)
The proteins in animal products like meat, eggs, and cheese are all complete (provide all essential amino acids in right proportion)
Essential Fatty Acids
`
Animals require fatty acids to synthesize a variety of cellular components (membrane phospholipids, signaling molecules, and storage fats)
Essential fatty acids are those that have to be gathered from the diet (animals lack the enzymes to form double bonds needed)
See Figure 41.2 pg. 895
Vitamins
Vitamins are organic molecules that are required in the diet in very small amounts--each vitamin has a diverse, unique function
13 vitamins have been identified for humans:
Water-soluble
B1 (thiamine)
B2 (riboflavin)
B3 (niacin)
B5 (pantothenic acid)
B6 (pyridoxine)
B7 (biotin)
B9 (folic acid)
B12 (cobalamin)
C (ascorbic acid)
Fat-soluble
A (retinol)
D
E (tocopherol)
K (phylloquinone)
Minerals
Dietary minerals are inorganic nutrients that are usually required in small amounts (ranging from >1mg-2,500mg per day) (i.e. iron and sulfur)
See Figure 41.2 pg. 895
Dietary Deficiencies
A diet that:
1) lacks 1+ essential nutrients
2) consistently supplies less chemical energy than is needed, will result in
malnutrition
(lack of adequate nutrition)
Deficiencies in Essential Nutrients
Insufficient intake of essential nutrients can cause deformities, disease, and even death
Protein deficiency is the most common type of malnutrition in humans
Undernutrition
A diet that can't provide adequate chemical energy results in undernutrition
When an animal is undernourished:
1) the body uses up stored carbohydrates and fat and then begins breaking down its own proteins for fuel
2) muscles begin to get smaller
3) brain may become protein deficient
3b) animal eventually dies