College Biology - Ecology

Test 1

Inference

Logical explanation using observations.

Observation

Something you use your senses to notice.

Independent Variable

What you change or control in an experiment to see if it affects something else (cause)

Dependent Variable

What you measure in an experiment or study to see if it changes in response to something else (effect)

Null Hypothesis

When there is no result in the experiment (things are often equal)

Population

The number of people living in a specific place

Population Density

A simple measure of how many people live in a specific area

Population Density Formula

Population Density = Total Population / Total Land Area

Growth Rate (R)

Growth Rate = Birth rate - Death rate

Logisitic Growth

Population stabilizes at a certain level (aka “K”)

Carrying Capacity (K)

Number of individuals in a population that an area can support

Exponential Growth

When a population grows faster over time because the number of new individuals added in each step is proportional to the current total

K-Selected Species

• Do not seek out new environments

• Population is relatively around “K”

• Care for their offspring

• Density dependent (as the population increases, limiting factors bring the population back down)

R-Selected Species

• Opportunist species

• Populations react to variations in environment

• Produce many offspring fast

• Do not provide care for young

• Density independent (population density does not affect the population)

Survivorship Curves

A graph that plots the number or proportion of individuals surviving in a population at each age

Survivorship Curves [X-Axis]

Relative Age (young, middle, old)

Survivorship Curves [Y-Axis]

Number of survivors

Three Types of Surviorship Curves

Type 1: K-Species

Type 3: R-Species

Communites

All the interacting populations of different species living and interacting in a particular area or habitat

Ecological Dominant

Species that are most abundant in certain ecosystems (there are the most of them)

Keystone Species

Species that may not be numerous but whose absence has a significant impact on the ecosystem.

Biodiversity

Range of species in a community

OR…

Diversity of species in a given area

Biodiversity Index

Biodiversity Index = # of different species / total # of organisms

Biodiversity Index (Transect Method)

Estimates the variety of species in an area by sampling along a straight line

[Example: (2/3 + 4/6 + 1/5) / 3]

Habitat

Physical surroundings of a species

Niche

An organism’s role in its enviroment

Interspecific Competition

Between two or more different species

Intraspecific Competition

Between members of the same species

Competitive Exclusion Principal

No two species can share the same vital resource for long periods of time

Resource Partitioning

Species divide up scare resources

AND…

Species adapt and specialize 

Symbiosis (has 4 types)

Two species live close together and at least one benefits

Symbiosis 1: Predator / Prey

One organism feeds on another (+, -)

Predators are dependent on prey

Symbiosis 2: Parasite / Host

Parasite feeds on or lives in the host (+, -) or (+, 0)

Symbiosis 3: Mutualism

Interaction between individuals of two different species that is beneficial to both (+, +)

Symbiosis 4: Commensalism

Interaction between two species in which one benefits while the other is neither harmed nor helped (+, 0)

Productivity

The rate at which living matter (biomass) is created by an ecosystem

Mimicry

One species evolved to assume the appearance of another

Example of Mimicry

Batesian vs. Mullerian

Primary Succession

Starting point is little to no life

• Soils lacks nutrients

• Begins with the arrival of a pioneer species

Secondary Succession

The final state of a habitat has been disturbed

• Life remains and the soil has nutrients

Pioneer Species

The first organism to settle in a brand new or disturbed habitat

Lichen

A complex life form that is a symbiotic partnership of two separate organisms, a fungus and an alga (A = food, F= home) & (+, +)

Climax Community

The stable community at the end of a succession

Aquatic Succession

A body of water gradually fills in with sediment and organic material, transforming into land-based ecosystem like a forest over a long period

Eutrophication

The gradual increase in the concentration of phosphorus, nitrogen, and other plant nutrients in an aging aquatic ecosystem such as a lake

Capture / Mark / Recapture

Wildlife estimation method where you capture a sample of animals, mark them with a tag or paint, and then release them back into the population (Later on, you’d catch them again)

Bd (Batrachochytrium dendrobatidis)

A deadly aquatic fungus that infects frogs and other amphibians