1 Lecture #8 – Introduction to Animal Structure and Function Images – the two most beautiful cats in the world, currently, as kittens and grownups
Dec 22, 2015
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Lecture #8 – Introduction to Animal Structure and Function
Images – the two most beautiful cats in the world, currently, as kittens and grownups
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Key Concepts
• What separates animals from other organisms?
• Introduction to structure and function relationships – the implications of being multicellular
• Hierarchical organization in animals
• Tissues
• Organ systems
• Bioenergetics and metabolic rates
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What do organisms have to do to make a living???
• Acquire resources (food, water)
• Eliminate waste products
• Exchange metabolic gasses
• Control internal conditions (homeostasis)
• Control function
• Control development
• Reproduce (optional for individuals, essential for evolutionary success)
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What makes an animal an animal?
• All are eukaryotic, multi-cellular, aerobic, and heterotrophic
• Most are mobile – exceptions???• Most are highly complex with many
specialized organs – exceptions???• Cells divide by cleavage• Excess carbohydrate stored as glycogen or
converted to fats• Most engage in sexual reproduction, some
also have asexual reproduction processes
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Structure and Function of Animal Systems
• Focus on human biology, but will use comparative approachComparisons between animals of differing
levels of complexity
• We will correlate structure with function, at all levels of organizationImportant theme in biology
• Start with intro to basic principlesThen discussions of various organ systems
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Table - the geological time scale
Critical Thinking
• Life has been on this planet for 3½ billion years!
• Until about 700 million years ago, all organisms were______________?
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It’s always fun to study the
geological time scale – it reveals the history of life
on earth
What happened here???
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Critical Thinking
• Life has been on this planet for 3½ billion years!
• Until about 700 million years ago, all organisms were single celled!!!
• The emergence of multi-cellularity allowed for organisms to adapt in complex ways to their environment
• The migration to land promoted even more diversification – about 450 million years ago
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Multi-cellularity imposes limitations, too
• In most multi-cellular organisms, not every cell is in contact with the external environmentMulti-cellular organisms develop complex
morphologies that reflect their environmentMulti-cellular organisms develop complex
mechanisms for resource/waste exchange with their environment
We saw these phenomena with plants – animals do the same thing
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Critical Thinking
• Terrestrial plants use a tight epidermis and a waxy cuticle to retain water
• What is the analogous structure in terrestrial animals???
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Critical Thinking
• Terrestrial plants use a tight epidermis and a waxy cuticle to retain water
• What is the analogous structure in terrestrial animals???
• The skin, and the oils that coat it
• Structure and function are related, and are the product of each species’ long history of evolutionary adaptations
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Critical Thinking
• Most animals (even many aquatic animals) urinate. Why???
• Most animals circulate metabolic waste products through a filtering system (such as our kidneys) and eliminate a liquid waste
• Do plants pee???
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Critical Thinking
• Most animals (even many aquatic animals) urinate. Why???
• Most animals circulate metabolic waste products through a filtering system (such as our kidneys) and eliminate a liquid waste
• Do plants pee???
• Plants don’t produce as much metabolic waste (they use more nitrogen) and they mostly either die back and recycle, or store the waste in isolated vacuoles or wood
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Images - convergent evolution of spindle-shaped swimmers
Constraints On Size And Shape:The physical environment affects animal evolution – as it does with all organisms
• Simple physicsFlight, soil burrowing,
swimming for speed…
• The physical environmentDense water or soil, thin air
• Often leads to convergent evolution of shape
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Diagram - 2 tissue layers in Cnidarians
Constraints On Size And Shape:The necessity of exchange with the
environment affects animal evolution….
• Resource/waste exchange with the environment
• Diffusion at the surface was characteristic of the earliest animalsLimits sizeLimits shape to thin, flat, openLimits complexityMostly quite simple animals
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Most animals have much more complex exchange systems
• Exchange occurs at internal epithelia
• Huge surface area is characteristic
• Fun factoids from humans:Lungs have 100 m2 of surface area (about ½ as big as
room)Small intestine has surface area of a tennis court80 km of tubules in a single kidney100,000 km of blood vessels = almost 3x circumference
of the earth
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Micrographs - lung and intestinal tissues
Critical Thinking
• How on earth do such large surface areas fit into our bodies???
• Folding! All these epithelial surfaces are highly convoluted
Small Intestine Tissue
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Exchange with environment is not direct for most animals
• Body is covered with waterproof surface• Complex organ systems exchange
materials• Organ systems are linked together, but not
usually directly• Most organ systems are separated by
interstitial fluid = a water-based solution that surrounds all cells in the animal body
• Transport occurs through the interstitial fluid
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Diagram - organization of organ systems showing indirect exchange through the interstitial fluid; same diagram on #29
Indirect exchange between organism and environment,
and between organ systems
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Critical Thinking
• Do nutrients leap from our breakfast cereal to our cells???
• Why do animals need nutrients anyways???
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Critical Thinking
• Do nutrients leap from our breakfast cereal to our cells???
• No – first they are extracted through digestion, then they diffuse to the cells through a fluid medium
• Why do animals need nutrients anyways???
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Critical Thinking
• Do nutrients leap from our breakfast cereal to our cells???
• No – first they are extracted through digestion, then they diffuse to the cells through a fluid medium
• Why do animals need nutrients anyways???
• Same as with plants – to build the macro-molecules that make the animal “work”
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Exchange with environment is not direct for complex animals
• Body is covered with waterproof surface• Complex organ systems exchange
materials• Organ systems are linked together, but not
usually directly• Organ systems are separated by
interstitial fluid = a water-based solution that surrounds all cells in the animal body
• Transport occurs through the interstitial fluid
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Indirect exchange between organ systems occurs via the interstitial
fluid
one big exception: the Malphigian
excretory tubules in insects are
directly connected to the digestive
tract
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Diagram - cells - organism in a zebra
All complex organisms have
a hierarchical organization
• Cells• Tissues• Organs• Organ systems• Organism
Form Reflects Function!!!
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Critical Thinking
• Think of your heart, or this zebra’s – how are structure and function related???
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Critical Thinking
• Think of your heart, or this zebra’s – how are structure and function related???
• Stretchy chambers to “store” blood
• Muscular chambers to “pump” blood
• Connected to vessels
• Result = circulation!!!
Yes, it really is often that simple and elegant
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Form and function are correlated from cells whole organism
• We learned about cells in 111….CellsTissuesOrgansOrgan systemsOrganism
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Epithelial Tissues
• Sheets of cells that cover the body surfaces and line many of the internal organs
• Base of epithelial tissue is attached to a basement membrane
• The free (exposed) surface has cells that are either cuboidal, columnar or squamous (tile shaped)
• Shape reflects function!• Some epithelia waterproof, some leak,
some secrete, some slough off….
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Diagram – sub-types of epithelial tissues
Epithelial tissues
Which do you think are
waterproof???Which
leaky???Which
secrete??? Which slough
off???
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Connective Tissues
• Cells held in a fibrous or fluid extra-cellular matrix Matrix generally secreted by the cells
• Many types and sub-types of connective tissueLoose – bind and shapeAdipose – store fatFibrous – strong connectionsCartilage – cushionsBone – support systemBlood – connects tissues to resources
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Critical Thinking
• What makes the “bones” of plants???
• Lignin gives rigid structure
• Cellulose allows positive pressure to build to keep cells plump
• Ground tissue gives additional structure to herbaceous plants
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Critical Thinking
• What makes the “blood” of plants???
• Resources are transported in the vascular tissues
• Some are “circulated” in phloem
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Muscle Tissue• Composed of cells that can contract • Skeletal = enable movement, attached to
bones by tendonsVoluntary = under conscious nervous system
control
• Cardiac = forms the heartInvoluntary
• Smooth or visceral = surround the digestive tract, other organsInvoluntary
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Nervous Tissue
• Transmits messages from one part of body to another
• Nerve cells have a central cell body + appendages that carry messages toward or away from the cell (dendrites/axons)
• Appendages may be a meter long in humans!
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Critical Thinking
• Do all animal tissue types have directly analogous tissue types in plants???
• Epithelial???
• Connective???
• Muscle???
• Nervous???
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Critical Thinking
• Do all animal tissue types have directly analogous tissue types in plants???
• Epithelial – certainly, though not internal
• Connective –sort of (vascular, ground)
• Muscle – not really – remember plants “move” by growing, other motions are related to water potential changes
• Nervous – no – plants respond primarily based on chemical signals
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Organs
• Composed of two or more types of tissues organized into a functional unit
• Tissues are often in layers, or they may be integrated throughout the organStomach has layers of epithelial, connective,
muscle, connectiveSkin has layers of epithelial, connective,
muscleAll tissues have blood vessels and nerve
tissues integrated
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Diagram – body cavities
Most animals have body cavities
• These are fluid filled spaces that cushion and suspend organs
• Sometimes they also give the body shape
• In vertebrates, many organs are held in place in the body cavity by layers of connective tissues (mesenteries) and sheets of muscle (diaphragm)
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Organ Systems: groups of related organs that maintain various
body functions
• Complex organ systems are present in all higher animals
• All organ systems are interdependentFunctions are coordinated (ex: digestive +
vascular)
• All systems work together to maintain homeostasis (~constant internal conditions, more on this later)
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Table – all the organ systems found in a complex animal
Organ Systems: most complex animals have 11 major organ
systems – image search for a table like this one
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Diagrams – closeups of the major organ systems; similar diagrams on next 4 slides
Digestive Circulatory
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Diagram – summary of organ systemsOrgan systems are integrated in both structure and function to
produce the whole organism
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Bioenergetic Principles Regulate Organism Activity
• Bioenergetics: the flow of energy through the animalControlled by energy sources vs. energy uses
(food intake vs. metabolism)
• Metabolic rates vary based on size, activity levels, homeostasis strategy and thermoregulation strategyImportant selection pressures include the
physical environment and interactions with other organisms
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Diagram – bioenergetics in an organismEnergy management: food supplies energy to fund metabolism,
maintain homeostasis, and support
activity
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Influences on Metabolic Rate
• Body sizeInverse relationship between size and
metabolic rate per unit massEvidence is clear; explanation is unclear
• Activity level
• Homeostasis strategyIt “costs” more to regulate
• Thermoregulation strategy
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Influences on Metabolic Rate
• Body sizeInverse relationship between size and
metabolic rate per unit massEvidence is clear; explanation is unclear
• Activity level
• Homeostasis strategyIt “costs” more to regulate
• Thermoregulation strategy
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Homeostasis
• Maintenance of constant internal conditions (actually, within a range of tolerance)
• Various control systems regulate temperature, salt concentrations, water content, pH, blood sugar, etc
• Most control systems rely on negative feedback loops = the results of a process inhibit that process process is self limiting
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Diagram – homeostasis
Most organisms regulate at least some components of their internal environment
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Homeostasis
• Maintenance of constant internal conditions (actually, within a range of tolerance)
• Various control systems regulate temperature, salt concentrations, water content, pH, blood sugar, etc
• Most control systems rely on negative feedback loops = the results of a process inhibit that process Process is self limiting
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Diagram – a mechanical representation of a negative feedback loop
Feedback Loops: thermostats and furnaces are a
non-living example
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Diagrams – representations of biological negative feedback loops
Many similar strategies for regulation of blood chemistry, blood sugar, body
temperature, etc etc etc
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Homeostasis is dynamic….
• All feedback loops are constantly monitored and levels are fluctuating within range
• Not all animals maintain stable internal conditionsRegulators expend metabolic energy to
maintain stabilityConformers don’t – internal values vary with
external conditionsSome animals regulate some conditions,
conform to others
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Influences on Metabolic Rate
• Body sizeInverse relationship between size and
metabolic rate per unit massEvidence is clear; explanation is unclear
• Activity level
• Homeostasis strategyIt “costs” more to regulate
• Thermoregulation strategy
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Thermoregulation
• All biochemical processes are sensitive to temperature
• Extreme temperatures can denature proteins or alter membrane function
• Animals regulate their internal temperature to maintain metabolic function
• Two main strategies have emergedEcothermy Endothermy
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Thermoregulation
• Ectothermic animals gain heat from the surrounding environment
• Most invertebrates, fishes, amphibians and reptilesLow metabolic rate when coldNot always able to be activeBehavior is often used to regulate body
temperature
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Graph – body temp vs. environmental temp in ectotherms vs. endotherms
Critical Thinking
• Are ectothermic animals cold blooded???
• NO!!! An ectotherm’s body temperature reflects its environment (with some exceptions)
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Critical Thinking
• What are the costs and benefits of ectothermy???
• Cost – limited activity and enduranceAnimals must remain warm to maintain active
cellular respiration When their body is cold, they cannot produce
enough ATP to be activeWhen cold, they can’t forage or escape!
• Benefits – low energy cost
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Thermoregulation
• Endothermic animals use energy to maintain a constant body temperature
• Primarily mammals and birdsHigh metabolic rate generates waste heat that
keeps the body warmMost endotherms also gain some heat from
their surroundings or behaviorsSome endotherms vary body temperature by
season or time of day (hibernation, estivation, diurnation)
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Critical Thinking
• What are the costs and benefits of endothermy???
• Cost – uses lots of energy10-30x more than same size ectotherm
• Benefits – allows for constant activityAlways able to forageAlways able to escape
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Most endotherms are terrestrial
• Moving on land requires more energy than moving in water (water supports)
• Land T fluctuates more than water T (high heat capacity of H2O)
• The development of endothermy was an important adaptation to the colonization of land
• Many terrestrial animals are ectothermic, but few aquatic animals are endothermic
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Graph – body temp vs. environmental temp in ectotherms vs. endotherms
Always active
Slow when it’s cold
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Both endo’s and ecto’s have many strategies to regulate body temperature
• Insulation
• Adjusting the rate of heat exchange with the environment
• Evaporative cooling
• Behavior
• Adjusting metabolic rate
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Many strategies to regulate body temperature
• Insulation
• Adjusting the rate of heat exchange with the environment
• Evaporative cooling
• Behavior
• Adjusting metabolic rate
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Adjusting the rate of heat exchange with the environment
• Constriction or dilation of surface blood vessels
• Raising of fur or feathers
• Fat accumulation
• Countercurrent heat exchange
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Critical Thinking
• How would changing blood vessel diameter change the rate of heat exchange???
• Alters the amount of warm blood that reaches the surface of the skinConstricting holds heatDilating releases heat
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Adjusting the rate of heat exchange with the environment
• Constriction or dilation of surface blood vessels
• Raising of fur or feathers
• Fat accumulation
• Countercurrent heat exchange
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Critical Thinking
• Why would raising the fur or feathers change the rate of heat exchange???
• Adds more of an insulating boundary layer around the skin
Image – fluffed bird
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Adjusting the rate of heat exchange with the environment
• Constriction or dilation of surface blood vessels
• Raising of fur or feathers
• Fat accumulation
• Countercurrent heat exchange
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Diagram – countercurrent blood flow in bird’s leg and dolphin’s fin
Countercurrent Exchange: arterial blood is warmer (comes from body core); warms adjacent venous
blood in extremities
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Diagram – countercurrent flow in deep muscles of fish
Adjusting the rate of heat exchange with the environment
• Some ectotherm fishes maintain higher temperatures in their deep swimming muscles with a heat exchanging pattern of blood flowIncreases aerobic
respiration (thus ATP production) in those muscles
Partial endotherms
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Many strategies to regulate body temperature
• Insulation
• Adjusting the rate of heat exchange with the environment
• Evaporative cooling
• Behavior
• Adjusting metabolic rate
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Many strategies to regulate body temperature
• Insulation
• Adjusting the rate of heat exchange with the environment
• Evaporative cooling
• Behavior
• Adjusting metabolic rate
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Image – dragonfly positioned for minimum solar exposure
Behavior
• Moving to shade/sun
• Moving into/out of water
• Restricting activity to night/day
• Regulating body posture to manage solar exposure
• Migrating
• Social behavior to share heat (bees)
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Many strategies to regulate body temperature
• Insulation
• Adjusting the rate of heat exchange with the environment
• Evaporative cooling
• Behavior
• Adjusting metabolic rate
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Adjusting metabolic rate
• Increases or decreases in muscular activity (shivering, active motion)
• Acclimation – many animals adjust to temperature changes throughout the seasons by changing enzyme type and quantity, altering lipids to keep membranes fluid
• Torpor – some animals react to predictable temperature and food supply fluctuations by entering a state of reduced metabolism (hibernation, etc)Daylength is the likely trigger
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Adjusting metabolic rate
• Increases or decreases in muscular activity (shivering, active motion)
• Acclimation – many animals adjust to temperature changes throughout the seasons by changing enzyme type and quantity, altering lipids to keep membranes fluid
• Torpor – some animals react to predictable temperature and food supply fluctuations by entering a state of reduced metabolism (hibernation, etc)Daylength is the likely trigger for seasonal torpor
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REVIEW: Both endo’s and ecto’s have many strategies to regulate body
temperature
• Insulation
• Adjusting the rate of heat exchange with the environment
• Evaporative cooling
• Behavior
• Adjusting metabolic rate