E c o l o g y

Ecological Levels of Organization
• Species: a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding.
• Population: a group of organisms belonging to the same species that are living in the same area
• Community: an interacting group of various species in a common location

Ecological Levels of Organization
• Ecosystem: a system formed by the interaction of a community of organisms with their environment.
An ecosystem Includes both biotic and abiotic factors
– Biotic Factors: Any living organism or factor created by a living organism that influences or an ecosystem.
– Abiotic Factors: a nonliving condition or thing, that influences or affects an ecosystem and the organisms in it

Ecological Levels of Organization
• Biome: A major ecological community adapted to a particular climate or environment over a large geographic area.
Major Biomes of Earth
1. Tropical Rain forest 2. Tropical Dry forest
3. Tropical Grassland/Savanna
5. Temperate Grassland
7. Taiga
4. Desert
6. Temperate Forest
8. Tundra

Ecological Levels of Organization
• Biosphere: The parts of the Earth where life can exist; includes the land, water and atmosphere.
Recap: Organization of Living Organisms
Cells → Tissues → Organ →
Organ System → Organism (Species) → Population→
Community
Biosphere
→ Ecosystem → Biome →

Ecological Succession
• Succession: the orderly process where a ecosystem changes over time.
– In each stage of succession a new plant community replaces the old plant community.
– Each stage of succession can support different organisms.

Ecological Succession
• Primary Succession: occurs on surfaces that did not previously support plant life, such as bare rock.
– What can cause primary succession to begin: volcanic eruptions and melting glaciers
– Pioneer species
(moss and lichens) can break down rock and form soil.

Ecological Succession
• Secondary Succession: occurs on surfaces that previously supported plant life, soil is already present.
– What can cause secondary succession to begin: forest fires, abandoned farmland, deforestation
– Grasses are often the first plant to appear and give rise to larger plants.
– Climax community: a stable and unchanging community established after succession

Community Interactions
Symbiosis: any relationship where two species live closely together.
There are 3 types of symbiotic relationships
1. Mutualism: A relationship that benefits both organisms involved.
– Explain the relationship between bees and flowers.

Community Interactions
2. Commensalism: A relationship where one organisms benefits and the other is unaffected.
3. Parasitism: A relationship where one organism
(parasite) benefits and the other organism (host) is harmed.

Community Interactions
• Competition: occurs when 2 or more individual simultaneously require a single resource that is in limited supply
– Competition harms both species that use a limited resource.
– Niche: The role or
“job” that a organism performs in its ecosystem.

Community Interactions
What happens when two species try to occupy the same niche?

Community Interactions
• Predation: the consumption of one organism (the prey) by another (predator)
– One organism is benefited and the other is harmed.
– How is predation different than symbiosis?
– Describe the relationship between predator and prey populations.

Community Interactions

Energy In An Ecosystem
• Food Chain: Shows the flow of energy from one organism to another.
• Energy moves from producers to primary consumer to secondary consumer, etc.
– Producers (autotrophs): make their own food through photosynthesis or chemosynthesis.
– Consumers (heterotrophs): obtain energy by feeding on producers or other consumers.
– Decomposers (heterotrophs): an organism that obtains its energy by breaking down dead and decaying matter.

Energy In An Ecosystem
Ecological pyramids: an illustration of the reduction in energy as you move through each trophic level in an ecosystem.
– Trophic Levels: any class of organisms that occupy the same position in a food chain

Energy In An Ecosystem
• Food web: interconnected food chains in an ecological community
What will happen to the killer whales if the disappeared from the ecosystem?
How will an increase in leopard seals affect the krill population?

Nutrient Cycles
Biogeochemical Cycles: describe the movement of elements through an ecosystem.
• Matter such as carbon, nitrogen, and water is recycled through the ecosystem.
• Energy from the sun is not recycled, instead it is lost as heat as it moves through an ecosystem.

Nutrient Cycles

Population Growth
Exponential Growth: When a population grows at a constant maximum rate.
• Small populations grow slowly
• The larger the population the faster it grows.
• Requires ideal conditions and unlimited resources.
Ex: One bacteria cell reproduces every 20 minutes. Assume unlimited resources . . .
– How many bacteria after 1 hour?
– How many bacteria after 2 hours?
– How many after one day?

Population Growth
Logistic Growth: The rate of population grow decreases and eventually stops due to a limiting factor.
• Carry Capacity: The maximum population size an ecosystem can support.
• Limiting factor: any biotic or abiotic factor that prevents a population from becoming too large.
– Density Dependent
Limiting Factors
– Density Independent
Limiting Factors
• Explain why the rate of population growth changes over time.

Population Growth
Observe the graph of human population growth over the past
2,000 years.
• Describe the pattern of human population growth.
• What would happen if the human population already surpassed the carry capacity of the
Earth?
• How has human overpopulation affected the environment?

Biodiversity
• Biodiversity is the variety of life forms in an area
– It can be measured in terms of genes, species or ecosystems.
• Ecology: is the study of the relationships between organisms and their environment.
– All biotic and abiotic factors in an ecosystem are connected.
– Human and natural disturbances can impact a single factor and cause the entire ecosystem to change.

Biodiversity
Invasive Species
• Species that are living outside their normal habitat.
• How do invasive species decrease biodiversity?
– They prey on native species.
– They outcompete native species for limited resources.

Biodiversity
Global Warming
• Greenhouse Effect
– Carbon dioxide, water vapor and methane are greenhouse gases.
– All trap heat and hold it next to the surface
– It is a natural process that keeps the temp suitable for life
• Global Warming
– Human activities, such as burning fossil fuels, increased the amount of CO2 in the atmosphere.
– A slight increase in temperature can have a large impact on the environment.

Biodiversity
Pollution
• Pollution is the addition of substances, objects, noise or light that causes harmful changes to an ecosystem.
• Extremely small concentrations of chemical pollutants have had a devastating impacts on the environment.
• Biological Magnification: the concentration of harmful chemicals in organisms increases as it moves up a food chain.

Biodiversity
Deforestation: The clearing of all trees from an area.

Biodiversity
Monocultures
• Monocultures: when a single type of crop is planted over a large area year after year.
• That one variety of crop that is grown may be highly susceptible to a certain type of pest or disease.
• Pesticides and fertilizers used to grow monoculture crops may be harmful to the environment.

Biodiversity
Eutrophication:
• Agricultural runoff adds nutrients to an aquatic ecosystem.
• This causes algae in the water to grow quickly (algal bloom)
• Algae will eventually die because of depletion nutrients and sunlight.
• Decomposition of the dead algae will remove oxygen from the water.
• Fish and other aquatic organisms will die of lack of oxygen.