1. 12.5 Interactions Between Individuals
SBI 4U1 – Population Dynamics

2. Learning Goals To know the different types of interactions
To understand what symbiosis is, and examples of its occurrence
To recognize the different types of defence mechanisms used by organisms

3. Coevolution Individuals in populations are not isolated
Coevolution occurs when one species evolves in response to changes in another

4. Types of Interactions Interaction Effects Example Predation +/-
Lion and antelope
Herbivory
Horses and grass
Mutualism*
+/+
Cows and intestinal bacteria
Parasitism*
Brood parasitism in cuckoo birds
Competition
-/-
Male-male deer competition during rut
Commensalism*
+/0
Moss growing on unaffected tree

5. Symbiosis
Mutualism, parasitism, and commensalism are types of symbiotic relationships
Sym = together, bio = life, sis = process
One species has a physically close association with another

6. Predation and Herbivory
Food is selected from a variety of resources
Specialists eat one or two types of food (e.g. pandas, koalas)
Generalists have much broader tastes and :. are more adaptable

7. Defence Mechanisms

8. Camouflage
Rock fish
Leaf tail Gecko

9. Chemical Defense Skunks
Bombardier beetle (shoots out fluid that is 100`C)
Vinegaroon (84% acetic acid shoots out)

10. Behavioural Defense
Octopus and ink
Rabbit freezing
Birds diving

11. mimicry Batesian: palatable mimics upalatable
Mullerian: 2+unpalatable species that share predators

12. Armour/spines
Armadillo

13. Competition Two main types of interspecific competition
Interference: direct harm (fighting; toxic chemicals)
Exploitative: reduces resources available
- Two or more species can’t coexist indefinitely if they rely on the same limiting resources

14. Niches
Fundamental niche: range of conditions that a population can hypothetically tolerate/use
Realized niche: range of conditions that a population actually uses

15. Resource Partitioning
Several species in the same area use different resources, or the same ones in different ways
E.g. plants gain nutrients from different depths of soil

16. Disturbing Ecosystem Relationships
Invasive Species
Ex. Zebra mussels, rock snot, pine beetle, emerald ash borer, rusty crayfish, strangling dog vine…

17. Examples of Symbioses!!! Ants and Aphids
Ants consume ‘honeydew’ from the aphids
Aphids are protected from predators by the ants

18. Fleas and Ticks
Fleas and ticks feed on the blood of other organisms

19. Oxpeckers and Large Mammals
Mammals get pests removed from their bodies
Oxpeckers are fed

20. Yucca and Yucca moths
Moths depend on yucca plants for food and shelter for larvae
Yucca plants depend on moths to distribute pollen for reproduction

21. Tapeworms and Mammals
Tapeworms attach to intestinal wall and consume food taken in by host

22. Bacteria and Plants Bacteria receive sugars from the plant
Plant receives nutrients from the bacteria when it fixes nitrogen (nitrogen is changed from N2 to NH3).

23. Clown Fish and Sea Anemone
Clown fish is protected by the nematocysts of the sea anemone

24. Vampire Bats
Bats depend on the blood of other organisms for food

25. Lichen Fungus and photosynthetic cyanobacteria or green algae
Extremophiles
Indicator species

26. Tongue-eating Louse Louse eats the tongue of a red snapper
Places itself where the tongue used to be
Acts as a tongue
Feeds on fish’s prey and its blood

27. Bot Flies Eggs laid under skin; sometimes via mosquito
Maggots live under skin; breathing tube protrudes from skin
Will leave when mature

28. Whale Barnacles Barnacles float around during larval stage
When suitable place is found, will attach to surface and develop into adult barnacle

29. Remoras
Remoras hitch-hike on the backs of larger organisms and they eat leftover scraps of food that are available

30. Boxer Crab and Sea Anemone
The Boxer Crab carries anemones around in its claws for protection
The anemone is able to scavenge food

31. Lampreys
Lamprey eels attach to a larger organism and feed off of its blood and/or flesh

32. Cattle Egrets Cattle Egrets follow herds of animals
They consume insects in the soil

33. Cuckoo Birds Female Cuckoos lay their eggs in the nests of other birds
The other birds raise the cuckoo fledgling

34. Bucket Orchid Glands secrete liquid that drips in the ‘bucket
Fragrance of flower attracts male euglossine bee
Bees try to gather dripping liquid to spread on body to attract females—bee cologne!

35. Flowers are open only a few days
Intense competition, head butting etc. between males to access limited mating perfume
Females will select male who has the right amount of perfume

36. Occasionally, male slips and falls into the bucket
The only exit is one lined with pollen sacs—pollen gathers on back when bee exits
If bee stumbles into another bucket flower, it will cross pollinate it, thus increasing the fitness of the flower
A very rare event

37. Different types of coryanthes attract different types of bees
Each species of bees rubs on a specific scent from a specific species of flower