1. Populations and Communities
Living Things and the Environment

2. Living Things & the Environment
Ecology - the study of how organisms interact with their environment.
Organism - a living thing.
Habitat - the specific environment that provides the things an organism needs to live, grow, and reproduce.

3. Living or Nonliving Parts of a Habitat
Biotic Factor - parts of a habitat that are living, or once living.
Examples - flowers, worm, frog, bacteria.
Abiotic Factor - nonliving part of a habitat.
Examples - water, sunlight, oxygen, soil, temperature.

4. How is an Ecosystem Organized?
Species - group of organisms that can mate with each other and reproduce.
Population - all members of one species in a particular area.
Community - all different populations that live together in an area.
Ecosystem - a community including its surrounding environment (abiotic factors)

5. Energy Flow in an Ecosystem
Each organism in an ecosystem fills the energy roles of producers, consumers, or decomposer.
Organisms that can make their own food are called PRODUCERS
The process through which producers make their own food (glucose) is called photosynthesis.

6. Energy Flow in an Ecosystem
CONSUMERS cannot make their own food, they will get it by feeding on other organisms.
Consumers are classified by what they eat in Herbivores, Carnivores, Omnivores, Scavenger.

7. Energy Flow in an Ecosystem
Herbivores: consumers that eat only plants.
Carnivores: consumers that eat only animals.
Omnivores: consumers that eat both plants and animals. Examples: bears, humans.
Scavenger: is a carnivore that feeds on the bodies of dead organisms. Examples: catfish and vultures.

8. Energy Flow in an Ecosystem
DECOMPOSERS: organisms that break down wastes and dead organisms and return the raw materials to the ecosystem.
They are nature’s recyclers.
Examples: mushrooms, bacteria, mold.

9. How does Energy move through an Ecosystem?
Energy moves through an ecosystem in the form of food when one organism eats another.
Food Chain: series of events in which one organism eats another and obtains energy.
Food Web: consists of many overlapping food chains in an ecosystem.

10. How does Energy move through an Ecosystem?
Energy Pyramid: is a diagram that shows the amount of energy that moves from one feeding level to another in a food web.
The most energy is available at the producer level of the pyramid.
As energy moves up in the pyramid, each level has less energy available than the level below.
Energy is measured in kilocalories (kcal)

11. 10% Rule in Ecology
An average of only 10% of the energy in one trophic level is passed to the next trophic level.
The remaining 90%, some is used up metabolically for survival and the rest is lost as body heat.
For example, if a plant receives 1000 Joules (J) from Sun, the animal who eats that, say a cow, would only get 10 % of 1000 J or 100 J. And the animal who eats that cow, say a human, will get 10 % of 100 J or 10 J from the cow.

12. Interactions among Living Things
Adaptations – a physical characteristic that helps an organism live successfully in their environment.
Example: cacti in the desert.
Niche – the role of an organism in its habitat. Examples:
Type of food the organism eats
How it obtains its food
What other organisms eat it
When and how an organism reproduces
Physical conditions it requires to survive

13. Interactions among Living Things
Two major types of interactions among organisms are competition and predation.
Competition – the struggle between two organism to survive as they attempt to use the same limited resource.
For example: plants can compete for soil nutrients, water, sunlight. Animals can compete for food, water, shelter, mates.

14. Interactions among Living Things
Predation – when one organism kills another for food or nutrients.
Predator – organism that does the killing.
Prey – organism that is killed.

15. Symbiotic Relationships
Symbiosis: any relationship in which two species live closely together and at least one of the species benefits.
Mutualism – both species benefit.
Example – Oxpeckers feed on parasitic ticks that infest black rhinoceros.
Commensalism – one species benefits and the other is neither helped nor harmed.
Example – Shark and remora. The remora receives food (scraps) from shark, but the shark is unaffected.
Parasitism – one species is benefited (parasite) and the other is harmed (host). Doesn’t kill because it needs the host to live.
Example – head lice, ringworm, tape worm, ticks.

16. Relationship
Species One
Species Two
Mutualism +
Commensalism O
Parasitism -

17. Population Fluctuation
Birth Rate - # of births in a population during a specific time.
Death Rate - # of deaths in a population during a specific time.
If birth rate is > than death rate, then population size increases.
If birth rate is < than death rate, then population size decreases.

18. Population Fluctuation
Immigration - organisms moving into a population.
Emigration - organisms moving out of a population.

19. Population Fluctuation
Population Density - # of individuals in an area of a specific size.
Population Density Equation:
Population Density= # individuals
Unit area

20. What Factors Limit Population Growth?
Limiting Factor - an environmental factor that causes a population to stop growing or decrease.
Examples: food, water, space, disease, shelter, parasitism, predation, nesting sites.
Carrying Capacity - the largest population that an area can support.