bio test 3 - homeostasis

osmoregulation

the active regulation of an organism’s water content

nitrogenous wastes

the nitrogen containing metabolic waste products of the breakdown of proteins and nucleic acids

osmosis

the passive diffusion of water across a membrane in response to a concentration gradient caused by an imbalance of molecules on either side of the membrane

nephron

The basic structural and functional unit of the kidney that filters the blood in order to regulate chemical concentrations, produce urine + eliminate nitrogenous waste

isotonic

when the cellular contents are of equal concentration

hypertonic

when the surroundings are more concentrated than the cellular contents. water will move OUT the cell and cell may shrivel up

hypotonic

when the surroundings are less concentrated than the cellular contents. water will move INTO the cell and cell may swell + burst

the 3 functions of the kidney

1. removal of nitrogenous wastes

2. regulation of water conc in blood

3. maintaining ion levels in blood

filtration

where fluid + solutes are filtered out of the blood in the glomerular capsule to form a glomerular filtrate

where does filtration occur

the glomerulus

reabsorption

the process of substances in the filtrate being absorbed back into the blood

where does reabsorption occur

loop of henle, collecting duct + distal and proximal convoluted tubule

osmoconformer

An organism in which the internal solute concentration changes with the concentration of solutes in the external environment e.g jellyfish,

osmoregulator

An organism that has specialised mechanisms for regulating internal water and solute concentrations, despite concentration changes in the external environment e.g birds, reptiles

examples of animals that secrete ammonia

Fish, Juvenile amphibians, Aquatic reptiles

solubility + water availability of ammonia

highly soluble and large amount of water availability to dilute ammonia

energy costs of ammonia

none to low

toxicity of ammonia

highly toxic

embryo development of ammonia

external development

advantage of ammonia as nitrogenous waste

large amount of water dilutes the toxicity of ammonia 

disadvantage of ammonia as nitrogenous waste

 Restricts these animals to these habitats 

examples of animals that secrete urea

mammals, most adult amphibians, marine bony fish

solubility + water availability of urea

moderate solubility + moderate water availability

energy costs of urea

moderate energy costs

toxicity of urea

moderately toxic

embryo development of urea

internal development in uterus

advantage of urea as nitrogenous waste

 Placental viviparity 

disadvantage of urea as nitrogenous waste

Lack of protein in diet, resulting in high rates of urea production 

examples of animals that secrete uric acid

birds + terrestrial reptiles

solubility + water availability of uric acid

insoluble + none to low water availability

energy costs of uric acid

high energy costs

toxicity of uric acid

least toxic

embryo development of uric acid

eggs in which the uric acid is stored in the eggshell as it is a hard layer + prevents the build up of nitrogenous wastes during development

advantage of uric acid as nitrogenous waste

Can have high protein diets 

disadvantage of uric acid as nitrogenous waste

lack of water

how does aestivation assist in animals retaining water

as metabolic reactions slow, and water is a product of metabolic reactions so slowing metabolic rate prevents less water from being produced + lost

how does burrowing assist in animals retaining water

• burrows have lower temps + higher humidity than open air so water loss is reduced

• burrow also traps exhaled water so there is less of a conc gradient between water vapour in air + animal which leads to less evaporation + less water loss

how does the hopping mouse reduce water loss

it has a bushy tail which it wraps around its face, trapping moisture from the air it breathes which saturates the air between face + tail, reducing water loss

2 problems with marine fish

1. Gains too many salts by drinking seawater + eating food

2. loses too much water via osmosis

solutions to help marine fish

• mouth open to constantly drink water

• actively pumps salt out via the gills

• little amount + concentrated urine to conserve water

2 problems with freshwater fish

1. Gains too much water via osmosis across the skin + when eating food containing water.

2. Loses too many salts via diffusion + in urine.

solutions to help freshwater fish

• mouth closed, does not drink

• actively pumps salt across gills into cells

• large, dilute amounts of urine

structural features for water balance

• waterproof or impermeable outer layer to reduce water loss e.g reptile scales

• acts as a barrier which prevents water loss via osmosis or evaporation

reptiles + birds physiological features for water balance

reabsorb water from the cloaca + excrete nitrogen as uric acid to save water

chiroleptes frog + notomys alexis (mouse) physiological features for water balance

• reduce urine production

• frog stores urine for dry seasons

• mouse has long loop of henle to concentrate urine + minimise water loss

camels physiological features for water balance

• do not need to drink water, gain it from food, stored fats or metabolism

• can tolerate very concentrated body fluids

marine vertebraes physiological features for water balance

• lose water via osmosis + drink sea water

• remove excess salt through gills + excrete concentrated waste

• sharks + rays retain urea to reduce water loss

freshwater vertebraes physiological features for water balance

• have more ions in body than env’t

• produce large amounts of dilute urine + actively absorb salts

• fish like salmon can adjust osmoregulation to suit env’t when moving between fresh + salt water

cohesion

the attractive force between water molecules

adhesion

the attractive force between water molecules + the inner walls of a vessel

root pressure

a force pushing on the water in the xylem, resulting from the active transport of salt ions into root hairs which causes osmosis to occur + water to move from soil into root hairs

capillary action

the movement of water within the spaces of a porous material or a narrow tube due to the forces of adhesion + cohesion

transpiration stream

the continuous flow of water from the roots to the leaves via xylem vessels due to the forces of adhesion, cohesion + root pressure

what is the relationship between potassium ions, conc gradient + osmosis

K+ ions are actively transported into the cell, creating a conc gradient. the guard cells then open and are able to take up water via osmosis and become turgid

how light affects the rate of transpiration

An inc in sunlight leads to an inc in transpiration due to warming the leaf + stimulating the opening of the stomata (active transport of ions into the guard cells can cause water to be absorbed via osmosis because of a conc gradient in the ions in solution); once the stomata are open, transpiration can start

how humidity affects the rate of transpiration

A dec in humidity leads to a higher water vapour conc gradient between the air at the surface of the leaf + the air outside the leaf. This inc diffusion of water vapour out of the leaf + evaporation from the leaf surface, which leads to an inc in water loss from the plant

how wind affects the rate of transpiration

An inc in wind leads to an inc in the rate of evaporation, which leads to an inc in the rate of transpiration, bc humid air near the stomata is being carried away, inc the water vapour conc gradient between the air at the surface of the leaf + the air outside the leaf

how temp affects the rate of transpiration

An inc in temperature inc the evaporation rate from the surface of the leaf, because of an inc in the water vapour conc gradient between the air at the surface of the leaf + the air outside the leaf. This leads to an increased rate of water loss from the plant

what are 4 features of a plant that help in conserving water

• trichomes

• reduced leaf S.A

• thick waxy cuticle

• sunken stomata

arid

an env’t characterised by a severe lack of available water that hinders the growth of most plant + animal life

xerophytes

a plant that has adapted to live in arid env’ts. it has developed specialised features that minimise water loss

what environments do xerophytes grow in

water limited + areas w/no flowing water e.g frozen arctic tundra

what is the problem for xerophytes

water moves passively along a conc gradient out the plant into the dry env’t. this means water vapour evaporates quickly + diffuses more quickly that a non arid env’t. plant cells can then become flaccid + wilt in dry env’t. if they lose too much water they cannot carry out photosynthesis which is required for evaporative cooling + needed for soil nutrients to dissolve + be absorbed by plant

thick waxy cuticle as a structural adaptation for xerophytes to reduce water loss

Impermeable to water, preventing evaporation + water loss. Stops uncontrolled evaporation through leaf cells

small leaf surface as a structural adaptation for xerophytes to reduce water loss

Fewer stomata, leading to reduced water loss. Less S.A for evaporation. Smaller S.A of leaf is exposed to the drying effects of the wind, reducing evaporation + reducing water loss.

sunken stomata as a structural adaptation for xerophytes to reduce water loss

Stomata in sunken pits within rolled leaves prevent water loss by inc the relative humidity in the vicinity of each stoma, dec the conc gradient and reducing evaporation + diffusion. Creates a micro climate.

stomata opening at night as a physioogical adaptation for xerophytes to reduce water loss

stomata are closed during the hottest part of the day, reducing water loss by transpiration/ evaporation (CO2 uptake occurs at night and it is then stored for use in photosynthesis during the day).

water storage as a physiological adaptation for xerophytes to reduce water loss

Plants store water in cells in fleshy stems or leaves instead of transpiring it out of plant, for use during dry periods; reduced water loss during hot dry periods

halophytes

a plant that has adapted to live in env’ts with high soil salinity

what environments do halophytes grow in

high soil salinity + high salt conc e.g salt marshes

what is the problem for halophytes

water will move out the plant via osmosis. this can reduce plant growth, germination can be hindered + plants can struggle w/a water deficit

salt accumulator halophytes

gather + store excess salt in their salt glands or in their central vacuoles

salt excluders halophytes

remove salt by ultra filtration through cell membrane + the endodermis

aerial roots as a structural adaptation for halophytes for salt regulation

Aid in respiration. The muddy, oxygen-poor soils that characterise these areas do not hold enough oxygen for these trees to effectively respire. Oxygen diffuses into the spongy tissue of the pneumatophores. They grow upwards out of the water or mud to reach the air

filtration structures as a structural adaptation for halophytes for salt regulation

Prevent salt from entering their roots. e.g Mangroves have an ultrafiltration system that can filter approximately 90% of sodium ions from the surrounding salt water. The 3 layers of the filtration system surrounding the roots trap sodium ions but allow water to pass through as it is pulled into the xylem

salt glands as a structural adaptation for halophytes for salt regulation

Salt is directed to plant surfaces, where salt glands secrete salt to reduce the salt content in the plant

concentrates/stores salts in vacuoles as a physiological adaptation for halophytes for salt regulation

Stores salt in the vacuoles of the fleshy stem segments or ‘beads’, which can have salt concs of 30–45%. The salt in the beads becomes highly conc, and they shrivel, die then drop off. This allows the rest of the plant to remain healthy

accumulates salt in leaves/barks as a physiological adaptation for halophytes for salt regulation

Salt is directed to older leaves or bark, where it accumulates. The leaves or bark eventually die and drop off, removing the salt from the plant.

homeostasis

the regulation of conditions inside the body to maintain a constant internal enviro in response to both internal + external conditions within tolerance limits

tolerance range

The range of a factor within which an organism can function + reproduce. if factors go outside this range, it may be fatal

zone of intolerance

The zone that is outside the tolerance range for survival 

zone of physiological stress

The zone that is outside the optimal range, but inside the tolerance range

optimal range

The narrower range, within an organism’s tolerance range for a particular factor, at which the organism functions best 

physiological stress

Stress caused when an organism experiences conditions outside its optimal range 

endotherm

An animal that uses metabolic processes to generate its own heat to maintain its internal temperature within the tolerance range

costs of endotherms

To maintain a stable internal temperature, they  may have a higher metabolic rate.  They need to spend more energy to maintain a  higher metabolic rate.  This results in higher food requirements + more time spent finding food 

benefits of endotherms

Body temperature is independent of external temp.This enables endotherms to live in more extreme env’ts. they can be active at night or more often during the day + in cold weather.  Being more active may reduce the chance of predation. 

ectotherm

An animal whose body temperature is determined by the external environment. Ectotherms rely on structures + behaviours for thermoregulation.

costs of ectotherms

Body temperature is dependent on the external environment.  These animals are limited to living in env’ts with less extreme temps. They cannot tolerate very high or very low external temps

benefits of ectotherms

Their heat source is mainly the env’t, so there are lower energy requirements for these animals.  they need to consume less food, can spend less time hunting for food.  They can tolerate larger fluctuations in their  internal body temp compared with endotherms. 

stimulus

a change in the internal or external env’t

receptor

detect the change in internal or external env’t. receptor may be internal or external

coordinating centre

a tissue or organ that receives messages from receptors and coordinates a response, then sends info to effector

effector

a muscle or gland that receives a message from the coordinating centre that a change in a stimulus has occurred, then carries out a response

response

the action of the effector that counteracts the stimulus

negative feedback

a message that counteracts the stimulus; returns the value back to normal or optimal value

chemoreceptor function

detects oxygen + ion levels. found internally

where are chemoreceptors found

in aorta + carotid arteries

osmoreceptor function

detects osmotic pressure in blood. found internally

osmoreceptor location

hypothalamus