The study of living organisms in the natural environment

How they interact with one another

How the interact with their nonliving environment

ENERGY

• At the core of every organism’s interactions with the environment is the need for energy to power life’s processes.

• Energy cannot be created, just used and transferred from different sources.

Energy starts with…

• Autotrophs: Organisms which can make their own complex, energy rich, organic molecules (e.g. photosynthesis)

– All plants are autotrophs

– Also known as primary producers

Then it moves to…

• Heterotrophs: organisms who must obtain complex, energy rich, organic compounds from other organisms.

– All animals are heterotrophs

– Also known as Consumers:

Specifically; herbivores,

carnivores, and omnivores

And it is recycled by….

• Detrivores:Heterotrophic organisms who ingest dead organic matter. (e.g. earthworms, woodlice, millipedes, vulchers)

– Also known as decomposers

Energy Flow through an Ecosystem

Producers Consumers Decomposers

Energy is transferred from one trophic level to the next and lost as heat.

10% Rule of Energy transfer: Only about 10% of the energy in one trophic level is transferred to the next level. The rest is lost as heat.

Tertiary Consumers

Secondary Consumers

Primary Consumers

Producers 10,000

kcal/m²/year

10 kcal/m²/year

Food Chain

• Single pathway of energy

Food Web

• Interconnecting food chains.

• Arrows demonstrate the pathway of energy. Arrow

must point to the consumer.

Community Interactions Symbiosis: Interaction between two or more

organisms

Predator-Prey

• When one organism (the predator) captures and feeds on another animal (the prey)

Mutualism

• Both organisms benefit

Parasitism

• One organism benefits, the other is harmed.

Commensalism

• One organism benefits the other is unharmed.

Characteristics of Populations

• Geographic distribution: the area inhabited

by a population • Example: 1 million square kilometers occupied by

migrating whales in the Pacific Ocean

• Density: the number of individuals per unit area

• Example: 150 bullfrogs per 3 square kilometers

• Growth Rate: the rate at which a population

changes • Example: In some developing countries, a baby is born

every 3 seconds.

Population Growth

• Birth Rate: The rate at which individuals are born into the population

• Death Rate: the rate at which individuals leave the population by dying.

Calculating Population Growth

Birth Rate- Death Rate = Population Growth

Ex: 700 turtles born in 1980

350 turtles died in 1980

700 turtles born – 350 turtles died= 350 turtles (Population Growth in1980)

–The point at which the growth slows or stops is known as the population’s carrying capacity or the largest number of individuals that environment can support.

Limits to Growth

• Limiting factor: something that causes a population growth to decrease.

Density Independent

• Affect all populations in similar ways, regardless of population size. (Abiotic Factors)

– Unusual weather, natural disasters, seasonal cycles, and certain human activities- such as damming rivers and clear cutting forests.

Density Dependent

• A limiting factor that depends on population size. (Biotic Factors)

– Competition: the more individuals living in an area the fewer available resources

– Predation: populations are often controlled by the predator-prey relationship.

– Parasitism and Disease: parasites can limit the growth of a population.

1. A group of organisms of the same species that interbreed and live in the same place

a. Community

b. Population

c. Organism

d. Species

2. A collection of interacting populations

a. community

b. population

c. organism

d. species

3. Interactions between biotic populations and abiotic factors in a community

a. community

b. biosphere

c. population

d. ecosystem

4. A single living thing

a. community

b. organism

c. population

d. ecosystem

5. Which is a biotic factor?

a. temperature

b. water

c. soil

d. plants

6. Organisms that use energy from the sun to make their own food are

a. producers

b. consumers

c. carnivores

d. omnivores

7. Animals that consume autotrophs for their food and energy are

a. producers

b. carnivores

c. herbivores

d. omnivores

8. Animals such as foxes that consume other animals for their food and energy

a. producers

b. herbivores

c. omnivores

d. carnivores

9. Animals such as bears that consume both plants and other animals for food and energy

a. producers

b. carnivores

c. herbivores

d. omnivores

Ecological Succession

• The replacement of one community by another in a single place over a period of time

Causes for Succession

• Primary Succession: occurs on a brand new surface that has never seen life.

– Ex: Island after a volcano eruption

Coastal sand dune

Secondary Succession

• Occurs on previously occupied land after a disturbance (anything that results in the removal of the existing communities)

– Ex: Fire, flood, deforestation, or competition with another organism

• Pioneer Species: first organism to appear in succession. Characterized as fast growing, rapidly reproducing, small in size and easily dispersed.

– Ex: Lichen- can survive in extreme conditions

• Late successional species: characterized as slow

growing, large in size, and longer lived.

• Climax Community: stable end community of succession