ECOLOGY & the ENVIRONMENT

ECOLOGY The study of interactions among organisms & their environment Ecologists divide environmental factors that influence organisms into 2 groups: ABIOTIC and BIOTIC.

ABIOTIC NONLIVING PARTS OF THE ENVIRONMENT Ex: Water, light, temperature, air, soil Air is a mixture of 3 main gases: oxygen, carbon dioxide, & nitrogen (used by plants & animals)

BIOTIC Living or once-living organisms in the environment Can be arranged into levels of organization:

1. organism 1 individual from a population Example: catfish

2. Population All the individuals of one species that live in the same area at the same time. Example: All the catfish living in a lake at the same time

3. community Populations of different species that interact in some way Example: Population of bass and all the species they interact with it

4. ecosystem All the communities in an area & the abiotic factors that affect them Example: lake, pond, coral reef, forest, etc.

5. Biome Large region with plants & animals well adapted to soil & climate of the region Example: Mountain, rainforests, tundra, desert, grasslands, temperate forests (where we live)

6. biosphere All the ecosystems on earth; the part of the earth that supports life Example: Top part of the earth’s crust, all the waters that cover the Earth’s surface, the surrounding atmosphere, & all the biomes.

Energy flow through an ecosystem Energy transfer: all energy comes from the sun and is transferred from one organism to another. Most of the interactions among members of different species occur when one organism feeds on another

When one organism is food for another organism, some of the energy in the first organism (the food) is transferred to the second organism (the eater).

Producers Organisms that take in & use energy from the sun or some other source to produce food. Examples: algae & plants

Consumers Ex.: frog, lion Organisms that take in energy when they feed on producers or other consumers. 1st level consumer: eats the producers 2nd level consumer: eats the 1st level consumer Ex.: frog, lion

Decomposers Ex.: bacteria, mushrooms (fungi) Organisms that take in energy (food) from dead organisms breaking down the remains of organisms & returning it to the soil so other plants can grow. Ex.: bacteria, mushrooms (fungi)

Niche: a species’ specific role in its community (habitat) Ex. A red fox is a predator that feeds on small mammals, amphibians & insects in its habitat

Movement of energy through a community can be diagrammed as a food chain or food web.

Food chain Simple way of showing how energy passes from one organism to another. Usually 3 or 4 links

Example of food chain: Water plant  insects  bluegill  bass Grass  grasshopper  frog  snake  owl

Food web Series of overlapping food chains that exist in an ecosystem More complete model of feeding relationships.

Energy pyramid Compares energy available at each level of the food chain in an ecosystem As you move from level to level, energy decreases.

Energy enters most ecosystems in the form of heat from the sun. Then it’s transferred into chemical energy by producers then passed to consumers as food. Then given back off as heat.

Cycles of matter Many important materials (water, carbon, & nitrogen) make up your body & cycle through the environment.

1. Water cycle Process of evaporation, condensation, & precipitation

2. Carbon cycle Plants absorb CO2 & combines it with water for their needs In photosynthesis, the plants use the carbon atoms from the CO2 to make sugars.

Carbon cycle continued… Animals eat the producers & other consumers and return the CO2 back into the air through respiration. Animals & plants die then carbon is returned back to soil during decomposition.

Nitrogen Cycle…. Nitrogen is “fixed” by bacteria in the soil then absorbed by plants & animals for their use.

Major Biomes of the world: 1. Aquatic: includes freshwater and saltwater (oceans) 2. Desert: 2 Kinds: hot/dry(little rain) and cold (snow), few plants grow in either and few animals live in them Ex. Great Basin in Utah, Sahara Desert in Northern Africa

3. Forest (rainforest, deciduous): lots of different vegetation & animals that live there, climate can be moderate temperatures or really cold rainforest Deciduous forest

4. Grasslands: mainly grasses, flowers and herbs grow here (not a lot of trees), animals, climate varies (can be humid/wet and hot summer/cold winter) Ex. Plains of Africa 5. Tundra- coldest biome, few plants and few animals, located in the Northern Hemisphere

Interactions among living organisms

1. Population size The number of individuals in a population

2. Population Density The number of individuals in a population that occupy a definite area

Classroom population density Length of room (m) X width (m) # of students =A (in m2) = how much space each person has

3. Population spacing How organisms are arranged in a given area Can be evenly, random, or clumped clumped EVEN random

4. Limiting factors Any biotic or abiotic factor that limits the number of individuals in a population Ex: drought, fewer plants, fewer nesting sites, predators

Food, water, & space are all factors in the growth populations in an ecosystem If an environment had no limiting factors, the population would INCREASE.

5. Carrying capacity Largest number of individuals of a species that an environment can support & maintain for a long period of time.