Ecology Chapter 20

Ecology: the study of how living things interact with their environment

Section one: Living things & the environment Habitat Where an organism lives that provides the things it needs to survive Different organisms need different habitats

Biotic Factors All the living things in an environment

ABIOTIC FACTORS All the nonliving things that affect organisms in their environment Examples include water, soil, sunlight, temperature & oxygen

Levels of Organization Start with an individual of one species All the individuals of one species living in a certain area is called a population.

All the different populations of species in an area make up a community

Community of organisms, along with their nonliving surroundings make up an ecosystem

Population Size 4 ways to determine population size: 1. Direct Observation: count all the members of a population 2. Indirect Observation: looking at signs of organisms instead of actual numbers Example: looking at swallow mud nests, count the number of entrance holes- on average each nest has 4 swallows- multiply

3. Sampling: if population is large or spread over a large area you can’t count them all, you have to make an estimate based on reasonable assumptions. 4. Mark and Recapture Studies: Capture animals and mark them. Then come back two weeks later and capture again. Count how many marked and unmarked that you count. Use a mathematical formula to calculate the estimated total population.

Changes in Population Size Birth & Death rate: birth rate higher then death rate- population gets bigger Death rate higher then birth rate= population gets smaller

Immigration & Emigration Population size changes when animals move in and out of the population Emigration is moving OUT of a population Immigration is moving INTO a population

Population Density How many organisms there are in a certain amount of area Pop. Density= # of individuals/ Unit area Example: 20 butterflies in 10 square meters of area, population density would be 2 butterflies per meter square

Limiting Factors Anything that stops a population from growing larger Food & water Space Temperature rainfall

Carrying Capacity The number of individual an area can support

Exponential Growth With unlimited resources, populations will grow unchecked: this is called exponential growth and is represented by a “J-Shaped” curve.

Logistic Growth Occurs when there are limiting factors that keep population growth balanced- called an S-Curve

Interactions Among Organisms Chapter 20

Predator/Prey One thing (predator) eats something else (prey)

Adaptations for feeding Ambush (camouflage) Teeth Night vision echolocation

Defense Strategies Camouflage False coloring- false eye- predators think organisms head is someplace else Warning coloration: Bright colors to tell predators they are poisonous Protective covering: porcupine

Camouflage

Mimicry

Warning Coloration

Symbiosis Process by which two animals of different species live in close contact with one another Three types of symbiotic relationships: Mutualism Commensalism Parasitism

Mutualism Both species benefit from living together Shark & teeth cleaning fish Cleaning shrimp & fish Crocodiles & cattle egrets Humans & E.coli bacteria

Commensalism One species benefits, other is neither harmed nor benefitted Example: red tailed hawk and saguaro cactus

Parasitism One species benefits and the other is harmed Leeches Ticks Hookworms Tapeworms botfly

Competition Due to limiting factors- when a resource is limited organisms must compete for it Usually the organism that competes the best reproduces more often & passes on those genes that allow it to be more successful- NATURAL SELECTION

Niche The role an organism plays in the environment- its lifestyle Different from habitat (where it lives)

Primary Succession Occurs in an area where NO soil or organisms exist The 1st species to populate that area is called a pioneer species Moss or lichen Break up the rocks and provide nutrients to the soil Over time seeds land in the soil and grow Grasses and shrubs often replace the pioneer plants

Secondary Succession Series of changes that occur in an area where the ecosystem has been disturbed, BUT soil and organisms are still present Natural disturbances: fire, flooding… Human disturbances: logging, farming…

Succession Series of predictable changes that occur in a community over time