Lecture #8 – Introduction to Animal Structure and Function

Lecture #8 – Introduction to Animal Structure and Function
Images – the two most beautiful cats in the world, currently, as kittens and grownups

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

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

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

What makes an animal an animal?
???

What makes an animal an animal?

Structure and Function of Animal Systems
Focus on human biology, but will use comparative approach Comparisons between animals of differing levels of complexity We will correlate structure with function, at all levels of organization Important theme in biology Start with intro to basic principles Then discussions of various organ systems

Critical Thinking Life has been on this planet for 3½ billion years!
Until about 700 million years ago, all organisms were______________? Table - the geological time scale

It’s always fun to study the geological time scale – it reveals the history of life on earth
What happened here???

Critical Thinking Life has been on this planet for 3½ billion years!
Until about 700 million years ago, all organisms were

Multi-cellularity imposes limitations, too
In most multi-cellular organisms, not every cell is in contact with the external environment Multi-cellular organisms develop complex morphologies that reflect their environment Multi-cellular organisms develop complex mechanisms for resource/waste exchange with their environment We saw these phenomena with plants – animals do the same thing

Critical Thinking Terrestrial plants use a tight epidermis and a waxy cuticle to retain water What is the analogous structure in terrestrial animals???

Critical Thinking Most animals (even many aquatic animals) urinate. Why??? Do plants pee???

Constraints On Size And Shape: The physical environment affects animal evolution – as it does with all organisms Simple physics Flight, soil burrowing, swimming for speed… The physical environment Dense water or soil, thin air Often leads to convergent evolution of shape Images - convergent evolution of spindle-shaped swimmers All organisms are constrained by their environment – selection pressures!!!!

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 animals Limits size Limits shape to thin, flat, open Limits complexity Mostly quite simple animals Diagram - 2 tissue layers in Cnidarians

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 court 80 km of tubules in a single kidney 100,000 km of blood vessels = almost 3x circumference of the earth

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

Critical Thinking How on earth do such large surface areas fit into our bodies??? Micrographs - lung and intestinal tissues Small Intestine Tissue

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

Indirect exchange between organism and environment, and between organ systems
Diagram - organization of organ systems showing indirect exchange through the interstitial fluid; same diagram on #29

Critical Thinking Do nutrients leap from our breakfast cereal to our cells??? Why do animals need nutrients anyways???

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

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

All complex organisms have a hierarchical organization
Diagram - cells - organism in a zebra Cells Tissues Organs Organ systems Organism All organisms are built in “layers” of complexity – different properties emerge as complexity increases Form Reflects Function!!!

Critical Thinking Think of your heart, or this zebra’s – how are structure and function related???

Form and function are correlated from cells  whole organism
We learned about cells in 111…. Cells Tissues Organs Organ systems Organism

Four major tissue types – read more in text
Diagram – tissue types

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….

Which do you think are waterproof???
Epithelial tissues Diagram – sub-types of epithelial tissues Which do you think are waterproof??? Which leaky??? Which secrete??? Which slough off??? Secreters have high volume to exposed surface area - columnar

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 tissue Loose – bind and shape Adipose – store fat Fibrous – strong connections Cartilage – cushions Bone – support system Blood – connects tissues to resources

Critical Thinking What makes the “bones” of plants???

Critical Thinking How about the blood???

Critical Thinking What makes the “blood” of plants???

Muscle Tissue Composed of cells that can contract
Skeletal = enable movement, attached to bones by tendons Voluntary = under conscious nervous system control Cardiac = forms the heart Involuntary Smooth or visceral = surround the digestive tract, other organs

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!

Critical Thinking Do all animal tissue types have directly analogous tissue types in plants??? Epithelial??? Connective??? Muscle??? Nervous???

Critical Thinking Do all animal tissue types have directly analogous tissue types in plants??? Epithelial – Connective – Muscle – Nervous –

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 organ Stomach has layers of epithelial, connective, muscle, connective Skin has layers of epithelial, connective, muscle All tissues have blood vessels and nerve tissues integrated

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) Diagram – body cavities

Organ Systems: groups of related organs that maintain various body functions
Complex organ systems are present in all higher animals All organ systems are interdependent Functions are coordinated (ex: digestive + vascular) All systems work together to maintain homeostasis (~constant internal conditions, more on this later)

Organ Systems: most complex animals have 11 major organ systems – image search for a table like this one Table – all the organ systems found in a complex animal

Digestive Circulatory
Diagrams – closeups of the major organ systems; similar diagrams on next 4 slides Digestive Circulatory

Respiratory Immune

Excretory Endocrine

Reproductive Nervous

Skeletal and Integumentary
Muscular

Organ systems are integrated in both structure and function to produce the whole organism
Diagram – summary of organ systems

Bioenergetic Principles Regulate Organism Activity
Bioenergetics: the flow of energy through the animal Controlled by energy sources vs. energy uses (food intake vs. metabolism) Metabolic rates vary based on size, activity levels, homeostasis strategy and thermoregulation strategy Important selection pressures include the physical environment and interactions with other organisms

Energy management: food supplies energy to fund metabolism, maintain homeostasis, and support activity Diagram – bioenergetics in an organism

Influences on Metabolic Rate
Body size Inverse relationship between size and metabolic rate per unit mass Evidence is clear; explanation is unclear Activity level Homeostasis strategy It “costs” more to regulate Thermoregulation strategy

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

Most organisms regulate at least some components of their internal environment
Diagram – homeostasis

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

Feedback Loops: thermostats and furnaces are a non-living example
Diagram – a mechanical representation of a negative feedback loop

Many similar strategies for regulation of blood chemistry, blood sugar, body temperature, etc etc etc Diagrams – representations of biological negative feedback loops

Homeostasis is dynamic….
All feedback loops are constantly monitored and levels are fluctuating within range Not all animals maintain stable internal conditions Regulators expend metabolic energy to maintain stability Conformers don’t – internal values vary with external conditions Some animals regulate some conditions, conform to others

Influences on Metabolic Rate
Body size Inverse relationship between size and metabolic rate per unit mass Evidence is clear; explanation is unclear Activity level Homeostasis strategy It “costs” more to regulate Thermoregulation strategy

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 emerged Ecothermy Endothermy

Thermoregulation Ectothermic animals gain heat from the surrounding environment Most invertebrates, fishes, amphibians and reptiles Low metabolic rate when cold Not always able to be active Behavior is often used to regulate body temperature

Critical Thinking Are ectothermic animals cold blooded???

Critical Thinking Are ectothermic animals cold blooded???
Graph – body temp vs. environmental temp in ectotherms vs. endotherms

Critical Thinking What are the costs and benefits of ectothermy???

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)

Critical Thinking What are the costs and benefits of endothermy???

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

Always active Slow when it’s cold
Graph – body temp vs. environmental temp in ectotherms vs. endotherms

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

Diagram – adipose tissue as insulation

Many strategies to regulate body temperature

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

Critical Thinking How would changing blood vessel diameter change the rate of heat exchange???

Critical Thinking How would raising the fur or feathers change the rate of heat exchange???

Critical Thinking Why would raising the fur or feathers change the rate of heat exchange??? Image – fluffed bird

Countercurrent Exchange: arterial blood is warmer (comes from body core); warms adjacent venous blood in extremities Diagram – countercurrent blood flow in bird’s leg and dolphin’s fin

Some ectotherm fishes maintain higher temperatures in their deep swimming muscles with a heat exchanging pattern of blood flow Increases aerobic respiration (thus ATP production) in those muscles Partial endotherms Diagram – countercurrent flow in deep muscles of fish

Sweating, panting, wetting….often linked to behaviors….
Images – animals panting and spraying

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) Image – dragonfly positioned for minimum solar exposure

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

Graph – change in a moth’s thorax temperature with pre-flight shivering
Shivering warms muscles in thorax – the point of wing attachment…

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

REVIEW: Both endo’s and ecto’s have many strategies to regulate body temperature

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

Lecture #8 – Introduction to Animal Structure and Function

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Lecture #8 – Introduction to Animal Structure and Function

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