BSC 2011 Exam 2 - Animals

Animal commonalities

All share a common ancestor = monophyletic group

• all are heterotrophic and multicellular

• most have internal digestion and movement via a nervous system (at some point in life)

Monoblastic and diploblastic animals

one or two tissues

• cnidarians

• placozoans

• ctenophores

• sponges

triploblastic animals/ bilaterians

three tissue layers: ectoderm (epidermal skin and nervous system) , mesoderm (muscle, connective tissue, bone blood, heart, kidney), and endoderm (lungs, digestive tract)

bilateral symmetry

• protostomes and deuterostomes

Protostomes

blastospore develops into mouth, then anus forms

dorsal digestive trace

ventral nerve chord

• arrow worms

• lophotrochozoans (mollusks, worms)

• ecdysozoa (arthropods, nematodes)

Deuterostomes

blastospore develops into the anus, then the mouth forms

ventral digestive tract

dorsal nerve chord

• echinoderms

• hemichordates

• chordates

Animal body plan characteristics

• symmetry

• body cavity structure

• segmentation

• appendages

• nervous system

Symmetry

• asymmetrical: no symmetry (sponges + placozoans)

• radial symmetry: symmetry around a central axis (independent in jellyfish + starfish)

• bilateral symmetry: can be divided along only one axis (humans, frogs, insects)

Body cavities/ coeloms

• acoelomates: no true body cavity (flatworms)

• pseudocoelomates: body cavity partially lined with mesoderm- only surround pseudocoel (roundworms)

• coelomates: body cavity fully lined with mesoderm (earthworms)

Segmentation

allows for specialization of body regions (alter body shape + precise movement)

• some animals are unsegmented (nematodes)

• some animals highly segmented (arthropod radiation due to segmentation —> highly successful))

Appendages

external appendages enhance ability of movement

• e.g. antennae, claws, mouthparts and reproductive organs

Nervous system

most organism have nervous systems to control parts of the body

• nerve nets: diffuse nervous systems in animals (cnidarians, ctenophores)

• vertebrates have organized peripheral and central nervous systems

• arthropods have groups of neurons (ganglia) in body segments

Early animal branches

cells in colonies began specializing for diff functions, leading to larger, more complex animals

• sponges: cells that function together, bodies of pores and channels for water circulation, choanocytes, some carnivorous (spicules)

• ctenophores: diploblastic, eight combe plates (ctenes) with beating cillia for locomotion

• placozoans: diploblastic, asymmetric, 4 cell types, no mouth/gut/nerves

• cnidarians: specialized stinging cells, nematocysts (harpoon-like structures) capture prey, gastrovascular cavity

Lophotrochozoans

lophophore: crown of ciliated tentacles for feeding/respiration

trocophore: distinct larval stage, ring of cilia for swimming/feeding

• Annelids: segmented worms, each segment has isolated coelom, permeable skin

• Mollusks: mantle covers internal organs (modified coelom), muscular foot, most have open circulatory system

• Flatworms lost coelom

Ecdysozoans

rigid outer cuticle secreted by epidermis - have to molt exoskeleton

• Nematodes: unsegmented worms

• Arthropods: paired appendages, very rigid exoskeleton (form monophyletic group with tardigrades + velvet worms)

1. Chelicerates: heads with two modified mouthparts (chelicerae): e.g. arachnids, seaspider, horseshoe crab

2. Mandibulates: mouthparts used for biting and chewing (mandibles) - Myriapods: segmented trunks, many paired legs (centipedes, millipedes) - Crustaceans: mainly aquatic arthropods, body divided into head, thorax, abdomen (shrimp, lobsters, crabs, barnacles) - Hexapods: six legs, body divided into head, thorax, abdomen, + gas exchange uses tracheae and spiracles (beetles, flies, bees, ants)

Echinoderms

sea star, sea urchins, sea cucumbers

• system of calcified internal plates forming internal skeleton

• system of water filled cannels connected to tube feet (used for gas exchange, locomotion, and feeding)

• bilateral symmetry —> changes to radial symmetry

Hemichordates

acorn worms, pterobranchs (secreted tubes)

• worm-like marine creatures

• three body parts: proboscis, collar, trunk

Chordates

all have three derived structures at some stage

1. dorsal hollow nerve cord

2. dorsal supporting rod (notochord)

3. post-anal tail

• tunicates: have all characteristics

• lancelets: lose notochord during metamorphosis to adult

• vertebrates: dorsal notochord develops into dorsal vertebral column, anterior skull with brain, well-developed circulatory system

Vertebrate Phylogeny

• hagfish are the closest relative to vertebrates

• evolution of jaws and teeth improved feeding efficiency - derived from anterior gill arches

Chondrichthyans

• jawed fish

• skeletons primarily composed of cartilage

• lack fins with supportive rays

Ray-finned fishes

• fins with supportive rays

• swim bladder (gas filled sacs supplementing gas exchange + improving buoyancy)

Lobe-limbed vertebrates

jointed appendages (paired) by single large bone

• Coelacanths: deep sea fish

• Lungfishes: both gills and lungs

• Tetrapods: four limbs (Amphibians + Amniotes)

Amphibians

caecilians, anurans (frogs + toads), salamanders

• live in moist environments (semi-permeable skin and eggs need water)

• direct developers: some amphibians can bypass tadpole stage

Amniotes

the amniote egg: key innovation of terrestrially adapted egg (protective aquatic environment)

• Reptiles: keratinized skin, scales

• Mammals: mammary glands, sweat glands, hair, four chambered heart, endothermy

Reptile clades

• Lepidosaurs: Squamates (lizards, snakes), Tautaras

• Turtles

• Archosaurs: Crocodilians (crocodilians, caimans, gators, gharials), Pterosaurs (extinct), Dinosaurs (extinct besides Aves)

Mammal clades

• Prototherians: produce milk without nipples, lay eggs

• Therians: milk with nipples, viviparous

Mass extinction effect on mammals

Mammals coexisted with dinosaurs for millions of years and were able to diversify after extinction of non-avian dinosaurs

Evolution of homeothermy, hair, and feather across the phylogeny of amniotes

• homeothermy developed independently in aves and mammals

• aves developed feathers from dinosaurs that had protofeathers

• mammals developed hair from skin glands

Relationship between bigger brains, smaller jaws, and neoteny

Humans retained juvenile features of apes like a globular skull, flat face, and small jaw into adulthood

• reduction in size of jaw muscles and supporting bones increased space for brain expansion

Animals are heterotrophs

animals require preformed organic molecules to obtain energy, build tissues, replace/grow cells

Essential nutrients

• amino acids

• fatty acids

• minerals

• vitamins (required in small quantities, cannot synthesize)

Metabolic rate defintion + measuring

the amount of chemical bond energy consumed and converted to heat per day

• measured by determining rate of oxygen consumption (1:1 ratio with production of heat)

Cellular respiration defintion and formula

process by which food is converted into energy

Food + O2 —> CO2 + H2O + Heat

Total vs Basal metabolic rates

• Basal metabolic rate: energy needed to do basic functions at rest, in comfortable environment, with no food consumed

• Total metabolic rate: basal + energy required for activity

  • humans-linear, fish-exponential, birds-u shaped

Scaling relationship

larger animals require more energy overall, but less per unit of body weight compared to smaller animals

Temperature conformity vs regulation

• Temperature conformity: animal’s internal environment permitted to vary with/match external environment

• Temperature regulation: animal’s internal environment stays constant while environment fluctuates

tradeoffs: regulation more energy intensive but allows for survival in larger range, conformity less energy intensive, but narrower range of survival

Interstitial fluids

cells in an animal’s body are bathed with tissue fluids, constituting their internal environment

Homeostasis

the process by which animals maintain a stable internal environment

Poikilotherms (ectotherms) vs homeotherms (endotherms)

both engage in behavioral thermoregulation

• Poikilotherms: variable body temps determined by environment

  • e.g. fish, reptiles, insects

• Homeotherms: maintain constant internal body temp

  • e.g. mammals, birds

Thermo-neutral zone

when metabolic rate is minimal, or leveled-off, when animals fall below or above this zone they have to increase metabolic rates to regulate temp

Homeothermic mechanisms

Cold

• shivering thermogenesis: skeletal muscles contract converting ATP to heat

• non-shivering thermogenesis: use brown adipose fat that uncouples oxidative phosphorylation to produce heat instead of ATP

• insulation: maintains body temp

• counter-current heat exchange: direct warm blood to body’s core

Hot

• evaporative cooling (sweating/panting) water absorbs heat energy to change state

Regulatory control systems

set point, feedback info, error signal

1. stimulus

2. sensors

3. control mechanism

4. effectors

negative feedback ex. thermoregulation (hypothalamus control, shivering effector)

positive feedback ex. oxytocin and uterine contractions during birth

Adaptations to cold extremes

• small animals use behavioral methods- make burrows or find caves to escape the cold

• larger animals use physiological defenses to prevent heat loss- good insulation (fat or hair), regional hypothermia keeps core constant temp but allows appendages to be colder (e.g. counter current heat exchange)

• both may hibernate- state of metabolic depression and thermal conformity

Adaptations to heat extremes

• small animals use behavioral methods- nocturnal lifestyle, burrow into ground, tuck in limbs (reduce SA exposed), shuttling between sunny and shady areas

• large animals use physiological defenses- high heat tolerance, no sweating to reduce water needs, countercurrent heat exchange to keep brain cool

freshwater fish osmoregulation

have greater concentration of ions in tissue than surrounding water (hyper-osmotic)

• gain water via osmosis through gills and skin (semipermeable)

• osmotic flooding must be checked to stop internal drowning

• kidney excretes excess water through dilute urine (and soluble salts replaced by food and absorption through chloride cells in gills)

saltwater fish osmoregulation

concentration of ions in the tissues is lower than that of surrounding water (hypo-osmotic)

• lose water through osmosis in gills and skin

• water loss compensated by drinking seawater

• remove excess salts using chloride cells in gills and by feces and urine

Osmotic conformers (iso-osmotic)

most marine invertebrates

• osmotic pressure of body fluids always same as surrounding water

• only survive in a narrow range of salinities

Marine air breathing vertebrates regulate salt by

extrarenal salt glands where salt is actively excreted using ATP

Phenotypic plasticity

an individual’s ability to display diff phenotypes in diff environments

• i.e. one genotype produces two or more phenotypes

Acclimation/acclimitization

phenotype changes from long-term exposure to a particular environment

Example of phenotypic plasticity (organs and biochemistry)

• Organs: Daphnia (water fleas) grow helmets and defensive swords in areas where predators are present

• Biochemistry: fish exposed to pollutants develop high levels of Cytochrome P450 enzymes to detoxify

Exogenous vs Endogenous timing

• Exogenous timing is mechanized by external environmental cues

• Endogenous timing is a self-contained metabolic mechanism to keep track of time

Circadian biological clock

• entrained to light-to-dark cycle: starts running at the same time each day, with a 24hr rest-activity cycle

• free-running: rest-activity cycle less than 24 hrs, activity will begin earlier each day

Benefits of an endogenous circadian clock

• adaptive by allowing animals to anticipate future events without external cues

• helps maintain a sun compass to compare perceived time of day with the sun’s position to determine directions

Bulk flow and Diffusion

Only two mechanisms for O2 movement, as there are no active transport mechanisms

• Diffusion: small-scale random movement of particles towards a state of equilibrium

• Bulk flow: large scale flow of matter from one place to another

  • incredibly important in delivering oxygen to cells quickly as diffusion is very slow

Process of mammalian respiration

1. Bulk flow- air is drawn through the mouth or nostrils to the lungs

2. Diffusion- air diffuses across to simple epithelium (alveolus and capillary) into the bloodstream

3. Bulk flow- heart pumps oxygenated blood through the body

4. Diffusion- oxygen diffuses from blood cells across two epithelium layers to target cells and through cytoplasm to mitochondria

Air vs. water as respiratory environments

• diffusion much faster through air

• in water, oxygen decreases with temp increase

• air has a much higher oxygen content than water

• higher energy expenditure to move water over respiratory surfaces

Gills vs lungs

• Gills evaginated (folded outward), surround environmental medium, unidirectional ventilation

• Lungs invaginated (folded inward), contain environmental medium, tidal ventilation

Animals without specialized breathing structures

some animals just use simple diffusion with low metabolic rates and cells close to body surface

Fish gills

• each gill arch has two rows of gill filaments

• fish pump/ram water unidirectionally through mouth, over gills, and out the opercular flaps

• blood and water flows through each lamella in a countercurrent system

Bird breathing system

• rigid lungs

• unidirectional ventilation via air sacs- don’t participate in gas exchange (parabronchi do)

• inhale: posterior air sacs expand with fresh air, exhale: air moves to parabronchi, inhale: stale air moves to anterior air sacs, exhale: air moves out the trachea

Insect tracheal breathing system

• spiracles in the abdomen open into tubules (tracheae)

• gas exchanged directly with atmosphere so circulatory system doesn’t play a role

• system limits size

Mammalian breathing system

• air enters lungs through two primary bronchi, then secondary bronchi, then bronchioles, and finally alveolar sacs (gas exchange occurs in alveoli)

  • cell walls extremely thin to minimize diffusion distance

• circulatory and respiratory systems work together: lungs take in O2 and pass it to blood to deliver it to tissues, and returns CO2 to be exhaled

Inhale as active and exhale as passive in humans

• inhalation: contraction of diaphragm expands thoracic cavity, pulling on and expanding the lungs to suck in air

• exhalation: diaphragm and muscles relax, allowing elastic recoil of lungs and thoracic activity to push air out

Negative feedback of CO2 levels

when CO2 levels increase, breathing rate increases to deliver more O2 to tissues and remove CO2

• carotid and aortic bodies in blood vessels are monitors for O2 + CO2 partial pressure —> send signals to brain to increase breathing

Ventilation def

actively moving the respiratory medium over the respiratory surface

Open circulatory system

blood exits the vessels as it flows through the body

• uses fluid hemolymph to directly bathe tissue cells in blood (no distinction between blood and interstitial fluid

• plays a larger role in oxygen transport for larger organisms than smaller (arthropods and mollusks)

• creates hydrostatic pressure

Closed circulatory system

blood always remains in the blood vessels

• found in annelids, cephalopods, and vertebrates

• more rapid and effective

1. heart pumps blood into arteries that branch out to microscopic capillaries

2. blood leaving tissues/organs flows into larger vessels until back to veins and heart

Arteries

carry blood away from heart

• operate under high pressure (elastic tissue and smooth muscle for stretch)

• branch to arterioles

• pulmonary artery exception- carries deoxygenated blood from heart to lungs

Veins

carry blood towards heart

• operate under low pressure

• one-way valves prevent backflow of blood

• pulmonary vein exception- carries oxygenated blood from lungs to heart

Capillaries

tiny vessels, primary sites of exchange between blood and body cells

• extremely thin walls with pores/gaps (efficient diffusion)

• capillary beds increase SA

Atrium vs. ventricle chambers

• atrium chamber receives blood

• ventricle chamber pumps blood

Microcirculation + vasomotor control

smooth muscles adjust arteriole diameter (allows redirection of blood from unneeded areas to needed areas)

• contraction causes vasoconstriction

• relaxation causes vasodilation

vasomotor mechanism: cuts blood flow to body and drops heart rate

Blood plasma

blood solution free of cells

• water and solutes (glucose, ions, waste, hormones, oxygen)

Blood cell types and platelets

• red (erythrocytes): hemoglobin and oxygen

• white (leukocytes): immune cells

• platelets: pinched off fragments of cell that aid blood clotting

Respiratory pigments

proteins greatly increasing the amount of oxygen that can be carried in the blood

• combines reversibly with oxygen

Red pigments

hemoglobin

• in most vertebrates

Blue pigments

hemocyanin

• spiders, crustaceans, mollusks, octopi, squid

• horseshoe crab blood clots when toxins are detected

Evolution of the vertebrate heart

vertebrate hearts are multi-chambered

1. pre-vertebrates: tube heart with closed vascular system

2. two-chambered heart: fish (single circulatory circuit)

3. three-chambered heart: amphibians (two atria one ventricle, pulmonary and systemic circuit)

4. partial separation: reptiles (partial septum in ventricle)

5. four-chambered heart: mammals, birds (pulmonary and systemic circuit)

Cardiac cycle phases

• Diastole (relaxation phase): ventricles relax and heart fills with blood, atria contracts completing ventricle filling

• Systole (contraction phase): ventricles contract and atrioventricular valves close, pressure builds in ventricles until aortic and pulmonary valves open and blood is is pumped out into the aorta and pulmonary circuits

Oxygen equilibrium curve

relationship between oxygen partial pressure and hemoglobin binding

• during rest, oxygen binding drops (unloading increases)

• during exercise, oxygen binding drops even more (unloading increases more)

total cross sectional area relation to blood velocity

as total cross sectional area of blood flow decreases, blood flow velocity increases

cross sectional area relative to blood velocity

as cross-sectional area increases (e.g. capillary beds) velocity falls due to increased flow resistance

• allows circulatory system to maximize exchange effectiveness

Sensory vs Motor neurons

• sensory neurons: carry signals from sense organs to CNS

• motor neurons: carry signals to muscle cells, stimulating contraction

CNS vs PNS

• Central nervous system: brain and spinal cord

  • ventral for arthropods

  • dorsal for vertebrates

  • interprets and processes perceived information

• Peripheral nervous system: all other parts of the system

  • neurons organized into nerves

  • perceives information

Autonomic vs Somatic nervous system

both part of the peripheral

• Autonomic regulates involuntary physiological processes

• Somatic causes voluntary contraction of skeletal muscles

Centralization vs Cephalization

• Centralization: grouping of nerve cells into a CNS

  • faster, better communication and coordination across the body

• Cephalization: nervous tissue highly concentrated in the anterior region

  • favors forward movement

types of nervous systems

• no nervous system: some simple organisms lack a nervous system

• nerve nets: simplest neural network (cnidarians and ctenophores)

• ganglia: neurons organized into clusters that process info

• brains: primary info processing center in sophisticated organisms

Neuron structure

• synapse: cell-to-cell contact point specialized for signal transmission (one-way)

• presynaptic cell: conducts signals into the synapse

• postsynaptic cell: conducts signals away from the synapse

• dendrites: carry signals to cell body

• cell body/soma: contains nucleus and organelles; integrates incoming signals

• axon: conducts action potentials away from the cell body

• presynaptic axon terminals: make synaptic contact with cells

Action potential

temporary depolarization of the cell membrane due to changes in ion distributions

• generated at one point and propagates over the whole membrane

Creation of neural signals

1. stimulus cause voltage-gated sodium channels to open and depolarize the membrane (sodium rushes in)

2. if the stimulus reaches the threshold potential an action potential is fired

3. membrane repolarizes as sodium-gated channels close and potassium-gated channels open (potassium leaks out)

• resting membrane potential caused by open potassium channels

Chemical synapses

communication between cells via chemicals instead of direct contact (synaptic cleft); most common

• neuromuscular junction (comm between neurons and muscles)

1. action potential stimulates influx of Calcium

2. neuron’s axon terminal releases neurotransmitter Acetylcholine

3. ACh crosses synaptic cleft to muscle cell

4. muscle cell’s receptors detect ACh and trigger action potential (chemical either reuptake or degraded)

Electric synapses

transmit signals directly between cells through gap junctions (extremely fast)

Reflexes

rapid, automatic motor response to stimulus

• reflex arc consist of the simple chain of neurons that give rise to reflexes (doesn’t require the brain)

Knee-jerk reflex

1. tap stretches tendon and stretch receptors activate

2. sensory neuron sends signal to spinal cord

3. sensory neuron directly activates motor neuron in the quad

4. quads contract and opposing muscle is inhibited causing the lower leg to jerk forward

Endocrine system

a system of ductless glands that produce endocrine secretions

• development, growth, reproduction, metabolism, stress responses

Evolution of chemical signaling

1. Unicellular eukaryotes: pheromones and quorum sensing

2. Cnidarians: early peptides and diffuse nerve nets

3. Bilaterians: compartmentalized endocrine tissues

4. Vertebrates: hormone axes

Hormone

chemical substance secreted into the bloodstream that influences other cell functions

• bind covalently to target cell receptors, trigger signal transduction

Three types of hormones

• Peptide and protein hormones

• Steroid hormones

• Amine hormones

Peptide and protein hormones

water soluble, easily transported in the blood

• packaged in vesicles and released via exocytosis

• polar so can’t cross cell membrane —> receptors on exterior of target cell

• e.g. insulin, growth hormones

Steroid hormones

synthesized from cholesterol

• lipid-soluble, pass through cell membrane —> intracellular receptors

• don’t absorb well in plasma —> require carrier proteins in the blood

• e.g. testosterone, estrogen, cortisol