Biology AS91603 Responses of plants and animals to their external environment

Tropism

A growth response of a plant toward or away from a stimulus

Phototropism

Growth of a plant shoot in response to light.

Gravitropism/Geotropism

Tropic movement in response to gravity

Chemotropism

Tropic movement in response to a chemical

Thigmotropism

A directional growth of a plant in response to touch.

Hydrotropism

a plants growth response to water; plant grows towards the water

Taxes

The movement of an animal in a specific direction in response to a stimulus

Positive chemotaxis

Movement of male moth towards female moth

Homing

The ability to find and return to the home site (in animals only)

Migration

The mass movement of organisms between two habitats (seasonal or regular)

Nastic response

Reversible, responsive movement of a plant that occurs independent of the direction of the stimulus

Thigmonasty

Sudden closing of Mimosa leaves when touched

Kinesis

Animals only: A non-directional response to a stimulus

Orthokinesis

The speed of the movement is related to intensity of stimulus

Klinokinesis

The amount of random turning is related to the intensity of stimulus

Biological clock

An internal timing system which controls (to some extent) timing of activities in organisms

Zeitgeber

External environmental cue by which an internal clock is reset

Circadian

Daily activity, approximately 24 hours

Circatidal

Tidal activity period, approximately 12.4 hours

Circalunar

Monthly activity period, 29 days

Circannual

Yearly activity period, approximately 360 days

Diurnal

Active during the day, inactive at night

Nocturnal

Active at night and at rest during the day

Crepuscular

Active at dawn and dusk

Arrhythmic

No regular pattern found in organisms in unchanging habitats eg. caves

Intraspecific

Competition between members of the same species

Interspecific

Competition between members of different species

Home range

A set area which animals seldom leave

Territory

Area that is defended by an animal

Pecking order

A social "pecking" order (or hierarchy) led by Alpha individual

Courtship

Series of signals exchanged between male and female and ending in mating

K-strategist

Organisms who produce and care for a small number of offspring

Pair bond

A stable relationship between animals of opposite sex that ensures mating

Parental care

Investment of resources by parents in the survival of offspring

Pheromone

Chemical used as a signal to other members of same species

Mimicry

Adaptive resemblance between unrelated species

Batesian mimicry

A harmless species mimics a harmful one

Mullerian mimicry

A mutual mimicry by two unpalatable species.

Instinct

Complex behaviour that is not modified by experience

Camouflage (crypsis)

Concealment method in which an animal is coloured to match the environment

Photoperiodism

Regulation by activity by day length

Phytochrome

Plant protein involved with the measurement of photoperiod

R-strategist

Organism which produces large number of offspring but gives them little care

Long day plant

Plant that flowers when day length exceeds a certain minimum value

Short day plant

Plants that flowers when day length is less than a certain minimum value

Entrainment

Process by which an internal clock becomes reset by rhythmic environmental factors

Free-running

Behaviour rhythm proceeding independently of external changes

Exogenous

Behaviour driven by external stimuli

Endogenous

Behaviour driven by internal stimuli

Day Neutral Plants (DNP)

Plants that flower independently of day length

Auxins

Plant growth hormones that promote growth by cell enlargement/elongation in plant shoots and germinating seeds

Commensalism

An interaction/relationship between two species that live together in which one species benefits from the association while the other is not significantly affected. (+ and 0)

Competition

The interaction/relationship between two or more organisms, populations, or species, that share some environmental resource when this is in short supply. Both organisms are harmed

Why do touch-me-not plants close when touched?

The leaves fall down when touched due to sudden changes in the turgidity of cells at the base of the leaves as the osmotic pressure suddenly decreases.

Explain auxin in shoots

Auxin is a plant hormone that promotes cell elongation and growth in the shoots. Higher concentrations of auxin causes cells to elongate, which changes the shoot’s direction of growth.