1 lecture #8 – introduction to animal structure and function

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Lecture #8 – Introduction to Animal Structure and Function

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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 all organisms have to do to make a living???

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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?

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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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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 environment

Dense water or soil, thin air• Often leads to convergent

evolution of shape

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Hands On

• Think of some other adaptations to habitat, food source or predators

• Name an animal – speculate on adaptive characteristicsWhat selection pressure might have resulted in

a structure or function?What structures or functions are phylogenetic?

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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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Critical Thinking

• How on earth do such large surface areas fit into our bodies???

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Micrographs - lung and intestinal tissues

Critical Thinking

• How on earth do such large surface areas fit into our bodies???

• Folding and branching! 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


• 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


• 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 Malpighian

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

Let’s talk about

tissues!!!

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Diagram – tissue types

Four major tissue types – read more in text

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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???

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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

• How about the blood???

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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 heart

Involuntary• 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,

muscleSkin 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 most 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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Respiratory Immune

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Excretory Nervous

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Reproductive Endocrine

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Skeletal and Integumentary

Muscular

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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 strategy

It “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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Diagram – homeostasis

Homeostasis mechanisms primarily control the interstitial fluid – the inside of the cell is very dynamic, depending on

metabolic activityFreeman is not completely accurate on this issue…..

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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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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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Critical Thinking

• Are ectothermic animals cold blooded???

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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???

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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 birds

High metabolic rate generates waste heat that keeps the body warm

Most endotherms also gain some heat from their surroundings or behaviors

Some 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???

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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

• Adjusting the rate of heat exchange with the environment

• 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• Behaviors

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Critical Thinking

• How would changing blood vessel diameter change the rate of 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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Critical Thinking

• How would raising the fur or feathers change the rate of 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

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Diagram – adipose tissue as insulation

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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


• 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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Image – dragonflies positioned for max or min 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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Images – animals panting and spraying

Sweating, panting, licking, spraying….often linked to

behaviors….

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Many strategies to regulate body temperature

• Adjusting the rate of heat exchange with the environment

• 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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Graph – change in a moth’s thorax temperature with pre-flight shivering

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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: 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

1 lecture #8 – introduction to animal structure and function

Documents

function slide

thing slide

terrestrial animals

plants animals

aquatic animals

evolutionary success

animal structure

analogous structure