1. EQ: How do the biotic and abiotic factors of an ecosystem interact?
Types of Interactions
EQ: How do the biotic and abiotic factors of an ecosystem interact?

2. Part 1: Limiting Factors
EQ: How do the biotic and abiotic factors of an ecosystem interact?

3. Types of Interactions Look at the seaweed forest on the left.
How many fish do you count?
How many seaweed plants can you see?
Why do you think there are more members of the seaweed population than members of the fish population?
Types of Interactions

4. Interactions with the Environment
Most living things produce more offspring than will survive.
A female frog will lay hundreds of eggs in a small pond
In a few months, the frog population will not increase appreciably.
T-P-S – Why?
Organisms, such as frogs, interact with the biotic and abiotic factors in its environment.
The environment will control the size of its population
Interactions with the Environment

5. Populations cannot grow without stopping, because the environment has a limited amount of food, water, living space and other resources
Limiting Factors

6. A resource that is so scarce that it limits the size of a population is called a limiting factor.
Food
Water
Space
Limiting Factors

7. Conditions that may limit the population of an ecosystem include, but are not limited to are:
Disease
Accidents
Natural Factors (fires, floods, etc.)
Starvation
Hunting
Predation
Limiting Factors

8. The largest population that an environment can support is known as its carrying capacity.
When a population grows larger than its carrying capacity, limiting factors in the environment cause individual organisms to die off and leave.
This causes a decrease in population
See What Limits Your Species PPT for lab
Carrying Capacity

9. EQ: How do the biotic and abiotic factors of an ecosystem interact?
Part 2: Interactions
EQ: How do the biotic and abiotic factors of an ecosystem interact?

10. Nature is amazing! For the most part, it keeps itself balanced (homeostasis) without human interference.
An ecosystem can only support a certain number of organisms (its carrying capacity).
To keep this number in check, each organism within an ecosystem has a specific role, or niche to fill.
As a result of the interactions between organisms as they carry out their roles, ecosystems generally stay balanced.
Limiting factors!
Interactions

11. Interactions Between Organisms
Ecologists have described four main ways that species interact:
Competition
Predator/Prey
Symbiotic
Coevolution
Interactions Between Organisms

12. When two or more individuals or populations try to use the same resource such as food, water, shelter, space or sunlight, it is called competition
Ex: Buffalo competing for mates
One wins, the other loses
Competition

13. Because resources are in limited supply in the environment, their use by one individual or population decreases the amount of resources available to other organisms
Competition

14. Many interactions between species consist of one organism eating another.
The organism that is being eaten is the prey.
The organism that eats the prey is called the predator.
Ex: Lion and zebra
Predator/Prey

15. Predator/Prey Result:
To survive, predators must be able to catch their prey.
To survive, prey must have methods and abilities to avoid capture.
These methods and abilities are called adaptations.
Predator/Prey

16. Some species have very close interactions with other species.
Symbiosis (symbiotic) is a close, long-term association between two or more organisms or species.
Symbiosis

17. In addition to the competitive relationships that help limit the population of an area, there are also cooperative relationships in an ecosystem that allow the habitat to function.
Those examples are:
Mutualism
Commensalism
Parasitism
Result: Organisms working in cooperative relationships
Symbiosis

18. The Earth is not static, meaning that it stays the same, but instead it is dynamic, or constantly and continuously changing.
Because the Earth itself is dynamic, the organisms that inhabit the Earth must change as well, or they will evolve out.
Another relationship is called coevolution, which is when two different species who are interdependent evolve together in order to perpetuate the species.
Coevolution

19. The term coevolution is used to describe cases where two (or more) species reciprocally affect each other’s evolution.
So for example, an evolutionary change in the structure of of a plant, might affect the structure of an herbivore that eats the plant
This in turn might affect the evolution of the plant, which might affect the evolution of the herbivore...and so on.
Example: Ant and acacia tree
Coevolution

20. Some Central American Acacia species have hollow thorns and pores at the bases of their leaves that secrete nectar
These hollow thorns are the exclusive nest-site of some species of ant that drink the nectar.
But the ants are not just taking advantage of the plant—they also defend their acacia plant against herbivores.
This system is probably the product of coevolution:
The plants would not have evolved hollow thorns or nectar pores unless their evolution had been affected by the ants,
And the ants would not have evolved herbivore defense behaviors unless their evolution had been affected by the plants.
Coevolution

21. Mutualism is a symbiotic relationship in which both organisms benefit.
Example: Insects and plants
What each organism gets:
Insects get the tasty nectar
Flower gets pollinated
Mutualism

22. A symbiotic relationship where one organism benefits, and the other is unaffected is called commensalism
Example: Clownfish and sea anemone
What each organism is getting:
Clownfish: protection
Anemone: doesn’t even notice
Commensalism

23. A symbiotic association in which one organism benefits and the other is harmed is called parasitism.
Example: Fleas and dogs
What each organism gets:
Fleas: food as it sucks blood from the dog
Dog: harmed
Parasitism