Biology 3.3 Plants and Animals

Intraspecific competition

Competition between members of the same species

Interspecific competition

Competition between members of different species

Tropism

To grow away from or towards a stimulus

Nastic responses

Non-directional plant movements triggered by external stimuli

Phytohormones

Natural chemical messengers produced by plants to regulate every aspect of their growth, development and stress responses

Abscisic acid

Promotes seed dormancy

Ethylene gas

Stimulates ripening fruit and initiates abscission of fruits and leaves

Gibberellin

Produced when water is absorbed by seed. Initiates germination and growth in seeds and buds

Produced in root tips and shoots and causes rapid cell elongation

Cytokinins

Stimulates cell division and promotes growth and development of chloroplasts

Auxins

Controls growth in roots and shoots through cell elongation

Exploitation

One organism harmed

One organism benefits

Parasitism

One organism harmed (host)

One organism benefits (parasite)

Mutualism

Both organisms benefit

Commensalism

One organism benefits

Other organism not affected

Antibiosis (contest competition

One organism harmed

One organism benefits

Symbiosis

Describing a close relationship

Obligate parasite

A parasite that entirely depends upon a host for its nourishment, reproduction, habitat and survival

Hemiparasite

An organism which lives on and deprives part of its nourishment from a different organism, and is partially self-supporting

Allelopathy

A form of competition where one organism produces biochemicals which influence the growth or survival of other organisms

Photoperiodism

The ability of an organism to measure the length of a day and use this to set its reproductive or development functions

Short photoperiod

Short day plant

Long photoperiod

Long day plant

Exogenous

Controlled by external cues

Endogenous

Internally controlled

Zeitgeber

Resets a biological clock

Freerunning

In the absence of external stimuli the biological clock is said to be freerunning

Vernalisation

Seeds require low temperatures to trigger growth

Stratification

Seeds require acid or fire treatment prior to germination

Entrainment

Using external cues to reset a biological clock