Ch. 3 - Introducing behaviour

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

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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

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Biotic factors

• Influence of living organisms
  • competition (intra and interspecific)
  • exploitation (predation, herbivory, parasitism)
  • mutualism

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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)
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Animal behaviour

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Plant responses

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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”

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