1. Ecosystems and Communities Chapter 4
Ecology
Ecosystems and Communities
Chapter 4

2. Populations are affected by both abiotic and biotic ecological pressures.
Habitat-
The area in which an organism lives

3. Niche: The organism’s place or role it takes in the ecosystem.
No two species can share the exact same niche in a habitat!
Shaded areas show where each species feeds (one factor that defines a niche).

4. Types of Symbiosis: Symbiosis: 1. Mutualism Parasitism Commensalism
Describes a close relationship between 2 organisms, in which at least one of the organisms involved benefits.
Types of Symbiosis:
1. Mutualism
Parasitism
Commensalism

5. Mutualism Both organisms benefit from the relationship.
A).Clown fish is provided a protective home and the sea anemone is provided food as the clownfish lures other fish toward the sea anemone.
B). Bees receive food (nectar), while the flower’s pollen is spread for reproduction.

6. Parasitism One organism benefits, and the other is harmed (host).
A).Ticks feed on the blood of the host in which they live. The closer together organisms live, the easier these parasites can spread through the population.
B). Make up one of your own

7. Commensalism
One organism benefits, and the other is neither helped nor harmed.
A). Barnacles live and grow on the bodies of various ocean organisms like whales. However, they do not help or cause any harm to them.
B). Make up one of your own.

8. -Parasitism -Mutualism Aphids feed on sugary sap from the plant.
Aphids are herded and protected by the ants because the ants feed on sugary excretions the aphids produce.
-Parasitism
-Mutualism

9. 4. PREDATION:
An interaction in which one organism captures and feeds on another organism

10. 5. COMPETITION:
when organisms attempt to use an ecological resource in the same place at the same time.
Could be over a mate, food, space, water etc. Anything that would affect survival.

11. The Carbon Cycle: a process through which the element carbon cycles through the environment.
1. In photosynthesis, producers remove CO2 gas from the atmosphere to make organic molecules (sugars)
2. Animals get organic molecules from plants & return CO2 gas to the atmosphere through respiration.
3. When plants and animals die in an ecosystem, CO2 gas is returned to the atmosphere during decomposition.
3. Fossil fuels (Coal, oil, natural gas which were once living organic material) when burned produce CO2 gas and this is returned to the atmosphere and increases the amount of CO2 gas in the air.
Draw this in your notes.

12. The Nitrogen Cycle
Producers (plants) absorb these forms through their roots.
Nitrogen fixation: actions by some bacteria & lightning change N2 gas into ammonia (NH4+) and nitrate ions (NO3-).
Consumers (herbivores) obtain nitrogen from the plants they eat.
Decomposers break down animal waste, dead animals, & dead plant material & return the nitrogen to the soil.
Other bacteria return nitrogen in the soil back to the atmosphere (denitrification)
Draw this in your notes.

13. Ecological Succession

14. Ecological Succession
The gradual replacement of an existing environment by another.
Primary Succession: when a community develops where there was none before.

15. Pioneer Organisms/Species : The first species to populate an area.

16. Secondary Succession: when an existing community is disturbed or destroyed without removing the soil and a new community begins.

17. Populations
Chapter 5

18. Three Characteristics of a Population
Geographic Distribution – describes area inhabited by a population
Density : # of individuals per unit area
Growth Rate : rate at which population changes in size

19. Factors that affect Size of a Population
Birth Rate
Death Rate
Immigration – People moving into an area
Emigration – People moving out of an area

20. Limits to a Population
1. Carrying Capacity: the number of organisms that an enviroment can support.
2. Limiting Factors: something that could cause a population growth to decrease. There are 2 types of limiting factors – Density-Dependent and Density-Independent.

21. Density-dependent Factors (affect larger populations)
Competition
Predation
Parasitism
Disease brought on not only by bacteria but also by stress, overcrowding etc.
(ex: Indian tigers fighting over land as it becomes less available, causes stress and they won’t mate)

22. Density-Independent Factors
Unusual Weather (drought, freeze)
Natural Disasters (Tsunami, Earthquake, Forest Fires, Floods)
Seasonal Cycles (Hurricanes)
Human Activities (deforestation, pollution, over-hunting, industrial growth, urban dev.)

23. Renewable & Non-Renewable Resources
Non-Renewable: can’t be replenished
Ex: fossil fuels such as coal, oil and natural gas
Renewable: can be regenerated or replenished but not necessarily unlimited.
Ex: trees, water

24. The variety of organisms in the biosphere
Biodiversity
The variety of organisms in the biosphere
Has provided us with a variety of foods, industrial products and medicines inc. painkillers, antibiotics, heart medications, antidepressants and anticancer drugs.
Threats to the Biodiversity can lead to species becoming endangered even extinct.
Examples of threats are altering habitats, overhunting, introduction toxic compounds into food webs and introduction of foreign species to new environments.