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 Tolerance and resistance.
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 K-strategists (K-selected) r-strategists (r-selected)
Development
Slow
Rapid
Adult Size
Large
Small
Number of Offspring
Few and large
Many and small
Generation time
Long
Short
Extra information
Limited by K
Live in stable environments
(Climax community)
Opportunistic species, fluctuating environments
(pioneers)

14. Survivorship Curves

15. Survivorship curves Type I Type II Type III
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) Diapause (P) Hibernation (P or 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. Osmoconformers Poikilotherms
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. 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.