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Interactions with the environment.

Explore how organisms adapt to external shifts, including behavioral and physiological responses. Learn about homeostasis, dormancy, and life histories in different environments. Understand the vital role of regulation and tolerance in maintaining stability.

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Interactions with the environment.

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  1. Interactions with the environment. AH Biology Environmental Biology

  2. Interactions with the environment • All organisms must be able to make internal adjustments in response to external changes in conditions • External – constant flux • Internal – range that must not be exceeded. • Organisms responses • Resist or tolerate • Regulation (homeostasis) • Avoidance / migration

  3. Behavioural responses • Changes in an organism’s behaviour which help them to survive changes in their environment. • Examples • Desert mammals • Nocturnal • Live in burrows during day • Hibernation or migration to avoid low temperatures

  4. Physiological responses • Changes in a way an organism’s body functions to enable it to survive in changing circumstances. • Organism can show a certain tolerance to its environment • Homeostasis

  5. What the specification says! Interactions with the environment AH Biology

  6. Responses • Two major types of responses of organisms to variation in environmental conditions • Conformation • regulation.

  7. Conformation • Conformation • osmoconformers • poikilotherms. • Tolerance and resistance. • Restricted habitat occupation of conformers.

  8. Dormancy • Dormancy • as a means of resisting or tolerating environmental adversity. • Predictive and consequential dormancy. • Forms of dormancy: • resting spores, • diapause, • hibernation, • aestivation.

  9. Regulation • homeostatic control in regulators as illustrated by osmoregulators and homeotherms. • The ability of regulators to occupy a wide range of habitats. • Energy costs of homeostasis.

  10. Variations in Life Histories Life history of an organism comprises its patterns of growth, development and reproduction.

  11. Growth and development • Rapid development • Leads to early reproduction and high rates of population increase • Periods of arrested development • Extend life cycle through periods of adverse environmental conditions • Longevity • Species with multiple breeding seasons

  12. Reproduction • Alternation of generations • “trade-off” reproduction and survival of parent • Some organisms reproduce once in a lifetime • Others have reproductive episodes through life • Clutch size • Large • Organisms who are unlikely to survive until the next season • Small • Organisms with a high probability of survival

  13. Life Histories

  14. Survivorship Curves

  15. Survivorship curves • Type I • flat during early and middle life and drops suddenly as death rate increases among the elderly. • This type of survivorship curve is associated with species such as humans and other large mammals that produce few offspring that are well cared for. • Type II • intermediate, with mortality more constant over life spans. • This type is seen in Hydra and the grey squirrels • Type III • very high death rates for the young, followed by lower death rates. • This type is often associated with organisms, such as oysters, that produce very many offspring but provide little or no care.

  16. Dormancy • Dormancy is a life history stage • Resting or tolerating periods of environmental adversity • Predictive (P) • Consequential (C) • Physiological state of minimal metabolic activity allowing an organism to avoid poor conditions or food shortages • Facultative • obligate

  17. Forms of dormancy • Resting spores (C) • Survive harsh conditions • Diapause (P) • Suspended development in insects • Hibernation (P or C) • Inactivity in mammals associated with cold winter conditions or food shortages • Aestivation (C) • Inactivity in hot, dry periods • State of torpor • Reduction of body temp. to ambient temp

  18. Homeostasis Negative Feedback

  19. Homeostasis • The process of maintaining stable internal environment • When the external environment varies there are two basic patterns of response • Conformation • Internal variables fluctuate with external environment • Limited environmental range • Regulation • Internal variables maintained at a constant level • Requires considerable energy • Less affected by environmental conditions

  20. Conformation Osmoconformers Poikilotherms

  21. Osmoconformers • Isosmotic (body tissues are isotonic with sea water) • Do not alter internal solute concentration • No osmotic gradient

  22. Poikilotherms • Variable internal temperatures • Animals obtain body heat from the environment (ectotherm)

  23. Ectotherm

  24. Endotherm and ectotherm

  25. Regulation Osmoregulation Homeotherms

  26. Osmoregulation • Body fluids not isotonic with the environment. • Use energy to regulate internal osmolarity • Revise Higher Biology SW and FW fish in hypotonic or hypertonic environments • Revise kangaroo rat, and adaptations of xerophytes

  27. Homeotherms • Relatively stable, raised internal temperatures • Revise human temperature regulation from higher biology • Endothermy carries an energy burden that opens up niches for foraging.

  28. Essay Question Give an account of homeostasis, discussing the differences between regulators and conformers.

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