A2 1 Biology

Homeostasis

The Maintenance of a constant internal environment within a living organism e.g. temp, pH and water

Negative feedback

1 type of control mechanism in which the condition being regulated is brought back to a set value as soon as it’s detected have parted from it e.g. waterbath

Excretion

The removal from the body of the harmful products of metabolism which would be toxic if allowed to accumulate

Osmoregulation

The maintaining of the osmotic potential of blood and tissue fluid by regulating the correct balance between the various solutes and water the kidney helps regulate the water potential of the blood through controlling the volume of urine produced and as a thirst response

Kidney

Purifies blood by ultrafiltration and reabsorption

Renal artery

allows blood to achieve a large blood supply

Net water potential

Water potential inside - water potential outside

Hypothalamus

Osmoreceptor cells are found and ADH is stored

prosterior lobe of the pituitary gland

ADH released

Resivoirs

Animal species that harbour viruses that cause disease in humans

Non-specific immunity

Quick response system. Phagocytes engulf foreign cells

Specific immunity

Cells and proteins in the blood and lymph attack, destroy and remove foreign bodies

Phagocytosis

Cell eating due to large uptake of particles by membrane devised vesicles carried out by polymorphs and macrophages

B-lymphocytes

Divide to produce plasma cells and secrete antibodies

B memory cells

Rapid response of plasma cells on reexposure

Memory T cells

Produce large clone of T lymphocytes on future reinfection

Killer T cells

Attack body cells, large pathogens and attach to antigens and destroy it by releasing hydrolytic enzymes

Helper T cells

Stimulate other cells involved in the immune response

Suppressor T cells

Regulation of the immune system by switching on and off immune responses blocking B and T cell responses

Central nervous system

Brain and spinal cord

Peripheral nervous system

Receptor cells, effectors, neurones

Myelin sheath

Insulating fatty layer that coats and insulates the axon and speeds transmission. No depolarisation occurs

Dendrites

Receive messages and carry them to the cell body

Nodes of ranvier

Increases transmission speed along the axon. depolarisation occurs here

Axon

Long extension of a nerve cell which carries information away from the cell body

Classifying receptors

Receptors are commonly classified according to the type of stimulus energy the detect

Mechanoreceptors

Detect changes in mechanical energy including movements, pressure, tension, gravity and sound waves

Thermoreceptors

Detect temp changes

Chemoreceptors

Detect chemical stimuli including taste and smell

Transduction

Receptors gather sensory information and convert it into a form of information that can be used by the animal

Transmission

Sensory neurones transmit nerve impulses from the receptors to the CNS

Processing

The CNS process the information so that appropriate responses can be made to environmental changes by motor neurones and effectors

Pupil

Gap within the iris which allows light to enter and reach the lens

Cornea

Front transparent part of the sclera where most refraction of light occurs

Suspensory ligaments

Ligaments that connect the ciliary body to the lens. Transfers tension in the wall of the eye to make the lens thinner

Ciliary muscle

Ring of muscle around the eye, suspensory ligaments extend from the ciliary body and hold the lens in place. It adjusts the shape of the eye to focus on light rays

Optic nerve

bundle of sensory nerve fibres that leave the retina and transmit impulses from the retina to the brain

Blind spot

Part of the retina where sensory neurones leave the eye. Contains no light sensitive cells

Fovea

Area isn the centre of the retina with a high density of cones. It provides the greatest visual activity and colour vision

Vitreous humour

Jelly like material between the lens and the back of the eye. Maintains the shape of the rear part of the eye and supports the lens

Retina

Inner layer containing light sensitive receptors cells. When stimulated rods and cones initiate impulses in associated neurones

Choroid

Layer of pigmented cells between the retina and the sclera. Contains blood vessels that supply the retina, preventing internal reflection of light

Sclera

Tough opaque tissue covering the eye continuous with transparent cornea at the front. Protects against damage and is the site of adjustment of the eye muscle

Conjunctiva

Thin transparent membrane covering the cornea. Protects the cornea from damage

Aqueous humour

Water fluid between cornea and lens. Maintains shape of front part of the eye

Lens

Transparent biconcave structure with refractive properties. Refracts light and focuses light rays on the retina

Iris

Contains circular and radial muscle. Adjusts the size of the pupil to control the amount of light entering the eye. Colour of the eye

Rhodopsin

In rod cells

Iodopsin

In cone cells

Resting potential

-70mv

Action potential

+40mv

Threshold

-40mv

Summation

The combining of the stimulatory effect to increase the generator potential e.g. rod cells

Nicotine

Stimulates the release of acetylcholine making action potentials more likely

Curare

Blocks receptors preventing transmission across synapse and subsequent loss of muscle control

Opioids

Block calcium ion channels resulting in less transmitter substance being released and action potentials less likely - opioids are effective pain killers as they reduce impulses coming from pain receptors

Effector

A structure which responds directly or indirectly to a stimulus

Skeletal muscle

Attached to the Skeleton

Cardiac muscle

In the wall of the heart

Neuromuscular junction

The synapse between neurones and muscle

Population

The number of organisms of a single interbreeding species within a specific area

Lag phase

Initial growth - slow

Log phase

Population grows at an increasing rate

Stationary phase

Carrying capacity (K) is reached and population has stopped growing

Death phase

Carrying capacity decreases and population begins to decline

Density independent

Factors affect all the plants or animals no matter how abundant the species is

Density dependent

Factors vary in how much they effect population depending on the size of the population (biotic)

Non - renewable resources

Population growth entering the stationary phase and the subsequent decline phase in a s-shaped growth curve due to nutrients not being replaced

Renewable resources

Nutrients are replaced

Fecundity

The reproductive capacity of individual females of a species

Death rate mortality

The rate at which individuals of a species die

Birth rate

The rate at which new individuals are produced

Immigration

Rate at which new individuals enter a community

Emigration rate

The rate at which individuals leave a community.

Mutualism

Where 2 organisms gain benefit from living together (+/+)

Competition

Relationship between 2 or more organisms to strive to obtain environmental resources when they are in short supply (-/-)

Intraspecific

Competition between members of the same species

Interspecific competition

Competition between 2 members of different species

Predation

Relationship between prey and predator (+/-)

Biological control

The use of natural predators, parasites or competitors to reduce the population numbers of pest species to a level where economic damage is no longer caused

Grazing

An interaction between a herbivore and a plant species (+/-)

Feeding

Transfer of energy between living things

Productivity

How much new material is produced

Secondary production

The energy used in production of new tissues in animals

Ecosystem

A community of organisms and their surroundings, the environment in which they live

Community

Consists on populations of different species which live in the same place at the same time and interact with each other

Habitat

Area which an individual lives

Microhabitat

A very small area which an individual lives

Succession

The changes in an ecosystem over time and the abiotic environment with important interactions between 2 components

Plant growth substances

Chemicals that occur naturally in plants in very low concentration

Node

The attachment site of a leaf or bud to a stem and the proportion between nodes is the internode

Pr

Absorbs red light

Off

Absorbs far-red light