Importance of response behaviour

Goal of any organism = survive and reproduce to contribute alleles to the gene pool

To survive, the organism must be able to detect and respond to changes in the environment

• Responses are adaptations for survival and reproduction through:

  • finding favourable conditions

  • ensuring sufficient supply of nutrients and necessary resources

  • reducing competition

  • avoiding predation/herbivory

  • finding mate of same species

Abiotic factors

• Non-living environmental factors

  • Temperature

  • Light intensity

  • Humidity

  • Wind speed

  • Salinity

  • pH

  • Water

  • Oxygen

  • Carbon dioxide

  • Mineral levels and substrate

• Organisms only inhabit areas where abiotic factors within range of physiological tolerance

• Physical tolerance: How much an organism can withstand

• Many abiotic factors are predictable as they are rhythmical

  • eg. daily and seasonal changes in day/night cycle

Biotic factors

• Influence of living organisms

  • competition (intra and interspecific)

  • exploitation (predation, herbivory, parasitism)

  • mutualism

Responding to the environment

• Organisms detect specific environmental stimuli using receptors (can range from simple nerve endings through specialised sensory cells to complex sense organs)

Animal behaviour

Plant responses

Adaptations

• Structural adaptations: adaptations to the structure of the organisms’ body ie. tail, hand, teeth, that increase its chance of survival and reproduction

• Behavioural adaptations: adaptations to the behaviour of the organism that increase its chance of survival and reproduction ie. homing response of domestic pigeons

• Physiological adaptations: adaptations to the chemical processes of an organism that increase its chance of survival and reproduction ie. anti-coagulants in the saliva of bloodsucking parasites

Ecological niche

• Niche: The way an organism has adapted in response to its habitat

  • Combination of an organism’s habitat (where it lives), how it lives there, and the role of the organism in its biological community

• Fundamental niche: The niche an organism would occupy if all necessary environmental conditions are present

• Limits of fundamental niche: Set by limits of the organism’s physiological tolerances to abiotic factors

• Realised niche: Actual niche that an organism occupies - much less extensive than the fundamental niche

• Limits of realised niche: Set by biotic factors such as interspecific competition or predation

• Vacant niche: A niche that has not been inhabited or opened up due to the extinction of a species previously occupying the niche.

• Overlap of niches between different specie cause interspecific competition

• Interspecific competition increases the more niches overlap

• Gauses’s competitive exclusion principle: applies when niches are sufficiently similar

  “No two species with identical niches can co-exist long in the same space”