1. Interactions within Communities

2. Populations of different species interact in a community
Some organisms rely on other organisms within the community for survival

3. Ecological Niches
An organism’s ecological characteristics, including use of and interaction with abiotic and biotic resources within its environment
Think of a habitat being one’s “address” and its ecological niche as its “occupation”
e.g. a lion’s niche includes what it eats, what eats it, the way it reproduces, the temperature range it tolerates, its habitat, behavioural responses, and all other factors that can describe its pattern of living

4. Ecological Niches
A Fundamental niche is the biological characteristics of the organism and the set of resources individuals in the population are theoretically capable of using under ideal conditions
Realized niche – the biological characteristics of the organism and the resources individuals in a population actually use under the prevailing environmental conditions

5. Interspecific competition
Interaction between individuals of different species for essential common resource(s) that are in limited supply
serves to restrict population growth
Can occur in two ways:
Interference competition –involves aggression between individuals of different species who fight over the same resource(s)
Exploitative competition – involves consumption of shared resources by individuals of different species, where consumption by one limits the resource availability to the other species

6. Interspecific competition
Gause’s Principle
competitive exclusion
No two species with similar requirements could coexist in exactly the same niche indefinitely
Population of weaker competitor can decline
One species could change its behaviour to survive using different resources
One population could migrate to another habitat

7. Resource partitioning
Avoidance of/reduction in competition for similar resources by individuals of different species occupying different non-overlapping ecological niches

8. Lake Malawi Cichlids
850 species from one ancestor!!

9. Mimicry Batesian mimicry Mullerian mimicry
Palatable / harmless species mimics unpalatable/harmful organism
Mullerian mimicry
Several animal species resemble one another and are all poisonous or dangerous

10. Predation
interspecific interaction by which population density of one species (predator) increases while population density of other species (prey) declines
time lags exist between responses to predator – prey interactions and their population sizes
sinusoidal curves exist in some predator-prey relationships

12. Defence Mechanisms - Plants
plants use both morphological defences
thorns, hooks, spines, needles
chemical defences
the defensive systems in plants act as selective agents which initiate the evolution of counter-adaptations in herbivore populations
these changes brought about by co-evolution between plants and insets can affect competition

13. Defence Mechanisms - Animals
sometimes employ passive defence mechanisms
e.g. hiding
others employ active defence mechanisms
e.g. fleeing
more costly to prey in terms of energy uses
other effective behavioural defences exist
e.g. alarm calls
e.g. camouflage (cryptic colouration)
e.g. visual warnings – in terms of chemical defences

14. Symbiosis Some organisms have obligatory mutualism
neither organism could grow or reproduce without each other

15. Mutualism – A symbiotic relationship in which both species benefit.

16. Mutualism Examples: Cowbirds and Large Animals
Termites and Trichonympha
Bees and Flowers

17. Cowbirds and Large Animals
The cowbird benefits by eating the ticks and mites off the large animal. The large animal benefits from have the parasites removed from them. The birds can also warn them of danger.

18. Termites and Trichonympha
You probably think termites eat wood; they do…in a way.
Termites can’t digest cellulose, which is the main component of wood.
Therefore, they get help from a protozoan called trichonympha.
This protozoan lives in the gut of the termite. It breaks down the cellulose for the termite. The trichonympha gets a free meal and shelter; the termite is able to eat and receive nutrients from the wood.

19. Termite and Trichonympha

20. Trichonympha

21. Bees and Pollen
Bees receive nectar from the flowers in order to make honey. As the bees collect nectar, they collect pollen on their body. As they fly to another flower, they pollinate it by dusting the pollen on the flowers stamen.

22. Commensalism
Commensalism – A symbiotic relationship in which one organism benefits and the other is not affected.
Examples:
Clown fish and sea anemones
Shark and remora

23. Clown Fish and Sea Anemones
The clown fish is immune to the stings of the sea anemones tentacles. The clown fish makes its home in the tentacles for protection. The clown fish gets shelter, but the sea anemone gets nothing.

24. Shark and Remora
The remora hangs around the shark picking up any scraps it may leave. The remora gets food while the shark gets nothing.

25. Parasitism
Parasitism – A symbiotic relationship in which one organism benefits but the other is harmed.

26. Parasitism
one organism benefits at the expense of another organism which is usually harmed
Parasites can be
Microparasites – microscopic in size with rapid reproduction rate (blood protozoans)
Macroparasites – larger organisms (tapeworms)
Endoparasites – live inside the body of their host
Ectoparasites – live and feed on the outside surface of their host (lice)
Social parasites manipulate the social behaviour of another species so that they can complete their life cycle

27. Parasitism
Examples:
Tapeworm and Humans
Cuckoo bird and warbler
Ticks

28. Tapeworm and Humans

29. Tapeworms and Humans

30. Tapeworms and Humans

31. Tapeworms and Humans

32. Cuckoo birds and warblers

33. Cuckoo and Warbler

34. Ticks

35. Tick

36. Even Athletes foot is a parasite

37. Parasitism

38. Parasitism

39. Symbiosis

40. Disruption of Community Equilibrium
interspecific interactions help maintain necessary equilibrium within complex and dynamic natural systems that sustain communities
A variety of disturbances affect this equilibrium
natural disasters
introduction of nonindigenous species
human influences
HOMEWORK P688 #1-7