Animal Physiology

By the end of this class you should understand:

• The system and mechanics of determining how organisms are related

• How to arrange animals on a phylogenetic tree

• The purpose and importance of the major physiological systems of animals

• The physiological differences between different groups of animals

• Why we must pee in a cup to get a job

Kingdom Animalia

• The first animals (similar to modern sponges) evolved around 1 billion years ago– Probably the first multicellular

organisms• Like all modern animals, they

had to eat food to grow and had no cell wall

• Animal diversity was limited until the Cambrian Explosion

Why the Cambrian Explosion?• The supercontinent Pannotia

(before Pangaea) broke up, restricting gene flow and creating new environments

• Homeotic genes were now evolved that controlled body plan

• Oxygen content in the atmosphere and ocean may have been rising– Animal cells all have mitochondria

so this would have benefitted them

Cambrian Explosion

Morphology and Phylogeny

• Quick Question: Who do you think is most closely related of these three organisms?– Seagull– Fruit Bat– Common Rat

• Can you place them into this phylogenetic tree?

Possible Arrangements

Common Ancestry

• We know the rat and bat are more closely related because they are both part of class mammalia– If you were paying attention yesterday…

• What this means is that they had a common ancestor with characteristics that they both have that the other animals don’t have– These predictions can be made by looking at cell

structures and embryos as well as bones

Identify Common Traits

Prediction of Ancestry

• The common ancestor of all eukaryotes:– Had membrane-bound organelles like

nuclei and mitochondria• The common ancestor of all animals:– Was multicellular, ate food and had no

cell wall• The common ancestor of the bilateria

group:– Had three layers of tissue as an embryo

and had bilateral symmetry

What about Echinoderms?• It’s true that echinoderms are part of

bilateria and yet they are radially symmetrical instead of bilaterally symmetrical– The embryo of the echinoderm is bilaterally

symmetrical and its opening becomes its anus

• Evidence suggests that embryo structure changes more slowly than symmetry, so it is more likely that echinoderms are closely related to chordates and lost their symmetry– The chance that they are closely related to

jellyfish but their embryos also develop like chordate embryos is considered very unlikely

Compare These Trees

• If this tree is correct, flying evolved twice, but having fur and making milk for babies evolved only once

• If this tree is correct, flying only evolved once, but having fur and making milk for babies evolved twice

Certainty

• Recall that in science nothing is every 100% certain, all we have is evidence

• The theory of evolution matches all data, and the tree of life is the best possible fit for all the probabilities– New fossils are still being discovered and they

often rewrite the tree of life– The “missing link” between humans and

chimpanzees was sought for a long time

Circulation

• The most important system in animal homeostasis is the circulatory system– Bring nutrients and oxygen to

all cells– Removes wastes from all cells

• Nutrients are put in by the digestive system

• Circulatory system must be cleaned by the excretory system (or renal system)

Circulation in Sponges• The simplest circulatory system is

in sponges– Probably similar to the first

circulatory system in our common ancestor

• Seawater is pumped through the body of the sponge by cells with flagella

• The cells of the sponge are filter feeders that grab food out of the seawater and eat it themselves– Essentially a colony of animal cells

cooperating

Circulation in Jellyfish• Phylum cnidaria has a more

advanced circulatory system based on the fact that they have multiple layers of tissues in their body

• Prey is paralyzed and dragged into its gut, and it is then dissolved into nutrients that diffuse to all the cells– Moved by seawater through the

tissues of the jellyfish– Waste products diffuse into the gut,

which eventually expels anything that wasn’t digested

Circulation in Bilateria

• In the most basic marine animals, ocean water is used as the circulatory system to allow things to move to all cells– This is inefficient, since ocean water doesn’t carry as

much oxygen• In addition to being bilaterally symmetrical, all

bilateria have circulatory organs that move a liquid through the body– Can keep oxygen-transporting materials in this fluid– Can keep this fluid clean and free of bacteria

Circulation in Annelids• Annelids like earthworms may

seem very primitive but they actually have a well-developed circulatory system

• Blood is kept in blood vessels and moved by several hearts– This is known as a closed

circulatory system• Blood passes around the digestive

tract to absorb nutrients• Wastes are collected in a pair of

small organs for every segment and excreted through the skin

Digestive Tract• An incomplete digestive system has just one

opening (like for jellyfish)– Same opening used for taking food in and waste out

• A complete digestive tract has two openings and materials pass in only one direction– Like ours!

Circulation in Mollusca• Mollusks have a large diversity in

their circulatory systems• Gastropods (snails) and Bivalves

(clams) have an open circulatory system– A heart pumps fluid through their body

but it is not contained in vessels and is called hemolymph

• Cephalopods have a closed circulatory system for more efficient delivery of nutrients– Nutrients leave the blood when it goes

through capillaries

Circulation in Arthropoda

• Arthropods all have an open circulatory system– Their exoskeleton is made of chitin,

which is a dense carbohydrate that makes their bodies impermeable to water

– Their organs are bathed in hemolymph which nourishes their cells

• Their circulation is poor since their heart is just stirring their fluids through their body

Circulation in Echinodermata

• Echinoderms are similar to early chordates but have developed radial symmetry

• Like sponges and unlike more advanced invertebrates, they use seawater as their circulatory system– They use a water vascular system to

nourish their body• They also use the water vascular

system to move by pumping water through tubes in their arms to make themselves move

Circulation in Fish

• Fish and other vertebrates all have a closed circulatory system

• Fish have a two-chambered heart which pumps blood over their gills and through their body in one big squeeze from the ventricle– Advantage: blood is always

oxygenated when it enters the body– Disadvantage: blood flow through

body is slower since it has already lost a lot of its pressure on the gills

Circulation in Amphibians and Reptiles

• Amphibians and most reptiles have a three-chambered heart

• Blood collects in two collecting chambers, one from the lungs or gills and the other from the body, then pumped by the well-muscled ventricle into tubes that lead back to both– Advantage: better circulation in

body– Disadvantage: some blood is not

oxygenated

Circulation in Birds and Mammals

• Crocodiles, birds and mammals have a four-chambered heart, which is the most advanced heart system for maximum efficiency

• Blood from the body is pumped to the lungs, blood from the lungs is pumped to the body– Advantage: best oxygen delivery

and best circulation– Disadvantage: requires a higher

metabolism

Excretory System Needs• All organisms must remove

waste chemicals in some way– The #1 waste to remove is

ammonia, which is produced when protein is metabolized to sugar or fat

• Marine organisms can simply secrete the ammonia into the water around them– Land animals cannot do this

because it wastes too much water

Behold the Kidney!

• The kidney is an organ that collects and stores wastes like ammonia (can be turned into urea to save water)– Can usually also secrete water or salt to

keep the salt/water balance in the blood safe

– Blood or hemolymph filtrate is called urine and is essentially all the wastes from blood

• Human kidneys are very effective since they must also balance water and salt levels

Advanced Excretory System• The more an animal must go without

water, the better its excretory system must be– Human kidneys are very good but no

match for desert animals!• A better excretory system is also

needed when an animal eats a lot of protein for energy– This is part of why the Atkin’s diet can

mess up your kidneys– Cats often develop kidney problems as

they age, since most other carnivores they are related to eat plants as well as meat

Why Pee In A Cup?

• When we take chemicals into our body that do not belong, they are broken down by the liver

• These drug by-products collect in the kidney and are removed by urination– Drug tests are basically a test for these

drug metabolites in the urine– These tests can be fooled by drinking a

crapload of vitamins and minerals, but that is super bad for your kidneys and they’ll know you did that anyway

See you in lab!

• More plants in lab today!