BSC 2011 Exam 2

what are some general characteristics of animals

-multicellularity, heterotrophic metabolism, internal digestion. movement and nervous system

common ancestor of animals

-probably a colonial flagellated protist, similar to choanoflagellates and sponges

-formation of colonies possibly occured because colonies are more efficient at pre capture than single cells

-cells in colonies began to specialize

why are choanoflagellate protist colonies and sponge choanocytes similar?

-evolutionary link between the two

-a sponge moves food containing water through its body by beating the flagella of its choanocytes

-water enters the sponge through small pores, passes into water canals, where the choanocytes capture food particles from the water

what is cleavage

-early cell divisions of an embryo

-patters of cleavage characterize major animal groups

what is radial cleavage

-yolk (provides energy) is evenly distributed throughout the egg cytoplasm,zygote and descendant cells divide completely and evenly (symmetrical)

what is spiral cleavage

-complex permutation of radial cleavage (new cells at angles to existing ones)

germ layers (diploblastic animals)

-have two cell layers, ectoderm (outer) and endoderm (inner)

germ layers (tripoblastic animals)

-have three cell layers, ectoderm, endoderm, and mesoderm (middle)

-form a clade

when do the germ layers form

-during gastrulation in the embryo (invagination)

what is gastrulation

-embryo is a hollow ball of cells that indents to form a cavity, the blastopore

bilaterians

-bilateral symmetry during embryonic development

-all triploblasts are bilaterians (have bilateral symmetry)

protostomes

-blastopore develops into the mouth; anus forms later

-ex. insects, snails

deuterostomes

-blastopore develops into the anus; mouth develops later

-ex. vertebrates and starfish

body plan

-general structure, arrangement of organ systems, and integrates functioning of body parts

-five features

• symmmetry, body cavity structure, segmentation, external appendages, nervous system

what is symmetry and the two types

-overall shape

-symmetrical- can be divided along at least one plane into similar halves

• radial-body parts arranged around a central axis

• bilateral- can be divided into mirror image halves on only one plane

-asymmetrical- no plane of symmetry (placozoans and sponges)

what is bilateral symmetry correlated with

-cephalization (has a head)

-concentration of sensory organs and nerve tissues at the anterior end or head

-seen as a more advanced trait

-evolutionary favored, anterior end encounters the environment first

acoelomate

-no fluid filled body cavity

-space between gut and body wall is filled with cells called mesenchyme; move by beating cilia

-ex. flatworm

pseudodocoelomate

-body cavity is a pseudocoel (fluid filled space)

-internal organs are suspended, no mesoderm surrounding interal organs

-ex. roundworm

coelomate

-body cavity is a coelom

-Develops within the mesoderm

-lined with a layer of muscular tissue, called the peritoneum

-enclosed on both the inside and the outside by mesoderm

-when muscles contract, can put pressure on fluid

ex. earthworm

how can body cavities function as hydrostatic skeletons

-when muscles contract, fluid is pushed to another part of the cavity, which causes that region to expand

segmentation

-facilitates specialization of body regions, allows animal to alter body shape and control movements precisely

• ex. our spine is segmented

• radiation of the arthopods was based on changes in a segmented body plan

appendages

-enhance an animal’s ability to move around; also include antennae, claws, mouthparts, and reproductive organs

nervous nets

-diffuse nervous systems in animals such as ctenophores and cnidarians

what kind of nervous systems do bilaterians have

-have well coordinated central nervous systems

• muscle action is coordinated to allow movement of appendages and body oarts

• sensory info is gathered and processed

which animal groups are not bilaterians

-sponges, ctenophores, placozoans, cnidarians

-most biologists agree that the sponges and ctenophores split first from the remaining animals

-large multicellular animals appear to have evolved several times in different lineages

characteristics of sponges

-have no distinct embryonic cell layers and no true organs

-have hard skeletal elements called spicules

• glass sponges and demosponges- spicules made of silicon dioxide

• calcareous sponges- spicules made of calcium carbonate

what are ctenophores

-comb jellies

-radial symmetry

-diploblasitc

-move by beating cilia arranged on eight comblike plates called ctenes

what are placozoans

-very simple, only 4 cell types

-diploblastic

-two life stages- pelagic (free) swimming stage and stage that adheres to surfaces

what are cnidarians

-jellyfishes, sea anemones, corals, hydrozoans

-diploblastic (more complex development)

-gastrovascular cavity- functions in digestion circulation, gas exchange, and as a hydrostatic skeleton

-life cycle with sessile polyp and motile medusa stages

-nematocysts- specialized harpoon like structures with toxins, used to capture large prey

cnidarian life cycle

1) Adult medusa produces gametes

2) Fertilization of the egg and sperm

3) The zygote develops into a planula larva (free-swimming)

4) The planula settles and develops into a polyp (stationary)

5) The polyp reproduces asexually, producing multiple young medusa

6) Young medusa grow into an adult

heterotrophs

-require preformed organic molecules as sources of energy and chemical building blocks

-obtain energy by breaking the chemical bonds of organic compunds obtained from other organisms

-build their tisssues from matter present in preexisitng organic compounds

-animals need chemical building blocks for growth and to replace cells throughout life

why organization is so important

-organization is the most essential attrubute of life

-2nd law of thermodynamics tells us that any organized system, left to itself, tends to lose organization and become more random

-animals need to obtain energy so they can do work to maintain their organization by combating the effects of the 2nd law of thermodynamics

-it takes energy to create and maintain organization

what are the 3 types of feeding

-predation

-suspension feeding- a method where an animal captures and eats tiny food particles floating in the water

-symbiosis

what is nutrition + its importance

-study of how animals meet their needs for both chemical substances and energy

-animals can interconvert some molecules

• ex. lipid molecules can be converted to carbs, but some molecules must be obtained, fully formed, from their food

essential nutrients

-required but cannot be synthesized by the animal

standard amino acids

-the 20 amino acids animals need to build proteins; animals can synthesize some of these (non-essential)

essential amino acids

-the ones that cannot be synthesized and must come from food

essential fatty acids

-including omega-3 and omega-6 fatty acids

essential vitamins

-vitamin a (vision), vitamin k (blood clotting) etc

essential minerals

-chemical elements that animals require in addition to C, O, H, and N

-ex. calcium and phosphorus are needing for bone, iodine is required for synthesizing thyroid hormones, iron is required to synthesize hemoglobin

how is the energy content of food measured

-can be measured by the amount of heat the food produces when completely burned in the presence of O2 producing CO2 and H20

-calorie- amount of heat needing to raise 1 gram of water by 1 degree celsius

metabolic rate

-amount of chemical bond energy consumed and coverted to heat per day

-animals with high metabolic rates need to eat more food per unit of time to replace the energy being consumed

-can be measured by determining rate of O2 consumption

-when organic matter is oxidized during aerobic metabolism, O2 is used while heat is produced

what are the 3 types of food molecules

-lipids, carbs, proteins

metabolic rate (humans, fish, birds)

-physical activity increases metabolic rate

-humans- metabolic rate increases linearly as running speed increases

-fish- metabolic rate increases exponentially because resistance posed by water increases exponentially

-bird- at low speed, metabolic rate is high just to stay airborne

basal metabolic rate (BMR) and its scaling relationships

-measured when the animal is in a comfortable thermal environment and has not eaten recently

-scaling relationships- animal characteristics as functions of body size

• BMR per gram of body weight decreases as animal size increases

• small mammals need more food per gram of body weight than large mammals do

regulation

-cells in an animal’s body are bathed with body fluids called tissue fluids (interstitial fluids) - the internal environment

-regulation occurs when the internal environment stays constant even as the external environment changes

• animas that do this are regulators

• regulation provides stability, but is energetically expensive, tend to increase metabolic rates

-in conformers, the internal environment varies so that is always matches the external environment

• energetically cheap

• animal’s cells must be able to cope with changes in their environment

intracellular and extracellular fluid

-intracellular fluid- fluid inside cells

-extracellular fluid- includes blood plasma and interstitial fluid

-fluid compartments are seperated by epithelia and cell membranes

what is the epithelium and simple epithelium

-sheet of epithelial cells that covers a body surface or organ or lines a body cavity

-simple epithelium: a single layer of cells on a non-living basement membrane; lines all blood vessels, intestines, and other tubules

function of the epithelium

-pumps ions between fluid on either side of the epithelium

-secretes substances such as horomones, mucus, digestive enzymes, milk, sweat

-absorbs nutrients from the gut

-serves sensory functions, including smell and taste

cell membrane and its functions

-thin layers separating the extra and intracellular fluids

-pumps ions between the intra and extracellular fluid

-play key roles in producing and receiving physiological signals

-controls diffusion of ions/molecules

levels of organization (tissue, organ, multi-organ system)

tissue- assemblage of cells of similar type

organ- two or more types of tissue with a defined strucutral relationship to each other

-multi-organ system- multiple organs working together

what is homeostasis

-refers to stability of the internal environment and the mechanisms that maintain it

-a parallel concept to regulation and has the same pros and cons; it is energetically expensive

homeotherms

-animals that maintain a constant internal body temperature (thermoregulation)

ex. mammals and birds

thermoneutral zone (TNZ)

-a range of external temperatures in which metabolic rate is minimal and does not change with external temperature

-outside the TNZ, the metabolic rate rises

what are poikilotherms or ectotherms

-body temperatures are variable and are determined by the external temperature

-Poikilotherms vary widely in their body temperature limits

-They can control body temperature through behavior, such as by positioning themselves in the sun or shade (behavioral thermoregulation)

-ex. alligator

the relationship between metabolic rate and external temperature

-Metabolic rates of homeotherms are higher than poikilotherms, especially when external temperatures are low

-Lower temp = higher metabolic rate

-super high temp = panting, sweating

homeotherm mechanisms

-can increase metabolic rate in cold environments

-shivering- skeletal muscles contract, and energy is converted from ATP to heat

-nonshivering thermogenesis- most mammals have brown adipose tissue in which oxidative phosphorylation is uncoupled from ATP production; energy goes to heat production instead

• smaller animals have more of this tissue

• occurs in specific locations in the body (in the places that are the most important)

-insulation- important for maintaining body temp, ex. fur and feathers

-blood flow patterns- can conserve heat

-evaporative cooling- water absorbs a lot of heat energy to change from liquid to gas state; sweating and panting allow water to evaporate from the body

negative feedback system

-control mechanism that activates effectors to bring a variable back into the normal (homeostatic) range

1) controlled variable- characteristic being controlled such as body temperature

2) sensors- detect current level or state, such as temperture receptors in the skin and brain

3) control mechanism- uses information from sensors to determine which effectors to activate. nerve cells of the hypthalamus in the brain are are temperature control mechanism

4) effectors- tissues or organs that can change the level of the controlled variable (ex. shivering muscles)

positive feedback

-deviations of a controlled variable from its existing level are increased or amplified (pushes father away from homeostasis)

-destabilizes a system, moving away from homeostasis, but can be useful if it is ultimately brought under control

-ex. childbirth

• stretching of the cervix —> pituitary releases oxytocin —> oxytocin causes stronger uterine contractions —> stretches the cervix more —> causes more oxytocin release —> stronger uterine contractions… ends with childbirth

types of environments

-specific environments- where they live and have evolved

-microhabitats (place/location)

-microenvironments (parameters of the location)

• places within a habitat that potentially differ from the habitat at large

-microclimate- climate conditons prevailing in a microenvironment

smaller animals and protective microenvironments

-small animals can enter small protective environments

-ex. lemming living under the snow

-easier for smaller animals to do this

small bodied animals behavioral and physiological defenses

-often deal with the stresses of an extreme environment by using behavior

• larger surface area to volume ratio

• higher metabolic rate- more energetically expensive to maintain body temperature

• easier to enter microenvironments

large bodied animals behavioral and physiological defenses

-often have fewer behavioral options; they depend more on physiological defenses to survive

phenotypic plasticity

-The ability of an organism to change its physical traits, behavior, or functions in response to its environment, without changing its underlying DNA

-ex. reindeer

• Reindeer have a much lower metabolic rate in winter compared to a human

• reindeer add insulation in winter, and regional hypothermia allows tissues in appendages to be cooler than the core tissues

regional hypothermia and countercurrent heat exhange system

-regional hypothermia- tissues in appendages doesn’t freeze, even when environmental temperatures are very low

-countercurrent heat exchange system- between arteries and veins in the limbs conserves heat

• keeps most of the heat in the body core, but prevents the paws from freezing

• ex. artic fox- heat is metered to foot pads so that the tissues cool to near the freezing point but never colder than freezing. feet are kept dry because they are too cold to melt snow or ice

hot dessert/ high temps behaviroal and psychological defenses

-mostly nocturnal- to avoid high temps

• ex. kangaroo rats

-countercurrent system

• keeps the brain cool

-large animals can tolerate a rise in core body temp

• gazelle

-burrows and small patches of shade, stay close to ground

• lizards

-live in colonies underground, forage during day for recently dead insects (to get water)

• desert ants

hibernation

-state of low body temperature and thermal conformity that persists for a long period of time in winter

-the animal allows its core body temp to match external temp

-animal lives on body fat or stored food

metabolic depression

-biochemically induced reduction of metabolic rate

supercooled state

-many insects can stabilize a supercooled state in which their body fluids do not freeze (fluids contain antifreeze)

-other insects species simply freeze soild and recover unharmed (cells contain antifreeze)

-many polar fish species are adapted to frigid waters and die if warmed to 5 degees celsius

-other species are adapted to warm tropical waters. different forms of key enzymes in the metabolic pathways function best at specific temperatures

internal respiration

-in mitochondria, oxygen (O2) is used as the final electron acceptor in aerobic respiration

external respiration

-animals obtain O2 from the environment, which then follows a pathway to the mitochondria

partial pressure

-the individual pressure exerted by a specific gas in a mixture of gases

-total atmospheric pressure = 760mmHg

• 79% N2

• 21% O2

-partial pressure of a gas equilibrates between air and liquid

-even though the partial pressues inside the gas and liquid are equal at equilibrium, the actual concentration is much lower in liquid than in air

the pathway for oxygen (steps)

1) air fills the lungs

2) oxygen diffuses across the alveolar epithelium and capitally epithelium

3) O2 diffuses down partial pressure (PP) gradient

• higher in lungs, lower in blood

4) O2 binds to hemoglobin (respiratory pigment) on red blood cells

5) O2 diffuses from blood into body cells

bulk flow definition

-passive flow of matter (material being carried within media) from one place to another

bulk flow and O2

-O2 and CO2 are transported by diffusion and bulk flow (no active transport)

-O2 is carried in the bulk flow of air into the lungs and alveoli

-O2 is also carried by the bulk flow of blood from capillaries to interstitial fluid

gas exchange membranes

-thin layers of tissue where respiratory gases move between the environment and the internal tissues

breathing (external respiration)

-process by which O2 and CO2 are transported between environment and gas exchange membrane

are lungs invaginated or evaginated

-invaginated (folded inwards) into the body and contain the environmental medium

are gills invaginated or evaginated

-evaginated (folded outward) from the body and are surrounded by the enviromental medium

ventilation

-bulk flow of air or water between the gas exchange membrane and the outside world

tidal ventilation

-air moves in and then out of the same passageways

• some fresh (O2-rich) and O2 depleted air mix

unidirectional (flow-through) ventilation

-in animals with gills water moves in a one-way stream across the gills (air and water comes in one opening and comes out another)

• no mixing of fresh and O2 depleted air

• more efficient at gas exchange

perfusion

-blood flow through capillaries or other small blood vessels of a tisse

diffusion in air vs water

-diffusion is much faster through air than water

• sea turtles lay eggs in the sand. eggs get plenty of O2, if the sand is moist not wet

-O2 solubility in water is low and descreases with increasing temperature

how do fish breathe

-fish gills have a large SA

-each gill has two rows of gill filaments, each with numerous secondary lamellae on its upper and lower surfaces

-a fish pumps water unidirectionally through mouth cavity and gill splits, over the gills and out from under the opercular flaps. blood flows through each lamella in the opposite direction, a countercurrent system

• Countercurrent flow- water moves across on way and oxygen moves across the opposite way

• Concurrent flow- same direction

surfactant

-inner surfaces of vertebrate lungs are coated with a lung surfactant that reduces surface tension and prevents the gas exchange tissue from sticking together

how do birds breathe

-unidirectional air flow to suppy O2 to tissues at high rates

• air sacs expand and contract acting like bellows to push air past gas exchange surfaces in the lungs

tracheal breathing system (insects and spiders)

-spiracles (openings) in the abdomen open into tubules called tracheae. the tubules branch in such a way that a gas-filled tubule comes close to every cell

-gases are exchanged directly with the atmosphere, so the circulatory systems plays litte role in O2 and CO2 transport

mammalian breathing system

-lung passages are highly branched

-the trachea branches into two primary bronchi, then into secondary bronchi, whcih end in alveolar sacs of epithelial tissue

-the wall of each alveolar sac consists of pocket like structures called alveoli, where gas exchange occurs

tidal volume

-the amount of air that moves in and out of the lungs per breath

respiratory minute volume

-total volume of air inhaled and exhaled per minute

residual volume

-lungs and airways are never completely empty some “stale” air is left behind

-prevents walls of lungs from sticking together (lung collapse)

inhalation

-contraction of the diaphragm expands the thoracic cavity, which pulls on the lungs and expands them, air is sucked in

exhalation

-the diaphragm and intercostal muscles relax, allowing elastic recoil of the lungs and thoracic cavity to push air out

PCO2 levels

-breathing is under negative feedback control by blood levels of CO2 (which lowers blood pH) and O2

• if PCO2 increases, H+ increases and pH falls, this is detected in the medulla oblongata and breathing is stimulated to increase respiratory minute volume

• If PO2 falls, chemoreceptors in the aorta and carotid arteries send nerve impulses to the medulla oblongata to stimulate increased breathing

what is in the circulatory system

-the heart, blood, blood vessels

circulatory system in vertebrates

-closed- blood remains within blood vessels

-the heart pumps blood into arteries, which branch into smaller arterioles, and evenually into capillaries of microscopic size

-as blood leaves tissues and organs, it flows into larger and larger vessels, the veins, back to the heart

-microcirculation (arterioles, capillaries, venules)

capillary walls and capillaries

-capillary walls

• consist of vascular endothelium (<1 micron thick)

• small blood cells must pass through one at a time

-capillaries

• found near every tissue cell and are the primary sites where O2, CO2, and other materials are exchanged between blood and cells

open circulatory system

-blood exits vessels as it flows through the body

-occurs in most arthropods and most mollusks

-no distinction between blood and interstitial fluids

• hemolymph (term sometimes used instead of blood)

blood plasma

-water and solutes such as glucose, ions, wastes, horomones, clotting proteins, and O2