BIOL215 Final

Ecosystem ecology

Study of communities (groups of populations) interactions with their environment (& abiotic factors)

Energy pathway

Flows from one end to another- isn’t “recycled”

Nutrient pathway (general)

Is cycled and recycled throughout communities

How is energy lost from one trophic level to another

heat, respiration

Where does free energy come from

the sun, chemical energy. very little is converted into usable forms

What transforms free energy into usable energy

Autotrophs/primary producers

Primary productivity

rate of capture of energy by ecosystems

Respiration

Oxidation rxn, process of converting carbohydrates into CO2

Photosynthesis

Reduction, CO2 into carbohydrates

How is primary productivity measured

by rate of e capture

• kcal/unit area/unit time

• watts/m2

• biomass promused

biomass

renewable organic material from plants and animals that can be used to generate energy

Relationship between biomass and primary productivity

Biomass is a standing amount, whereas primary productivity is a rate. The biomass of two communities could be the same, while the rate of primary productivity could differ. 

Gross primary production GPP

total E fixed by plants per unit time. Some of this energy is used for respiration

Net primary production (NPP)

Energy fixed by photosynthesis- Energy lost from respiration

Methods of measuring productivity

Harvest method, Gas exchange

Method of measuring productivity over long intervals

Harvest method

Method of measuring productivity over short intervals

Gas exchange

Harvest method

Way of measuring productivity via change in biomass. Equation is (B1-B2)/t

Gas exchange method

Way of measuring productivity, typically in aquatic environments. Equation is (rate of gas production) - (rate of gas consumption)

Difference between calculating GPP v. NPP

GPP= change in biomass + other ways + energy lost to respiration

NPP= change in biomass + other ways

Liebig’s law of the minimum

the rate of any biological process is limited by the factor that is in least amount relative to the organism’s requirement, yield limited by single resource

Evapotranspiration

the amount of water that evaporates off of and is transpired by plants off a landscape, positive rls. between evapotranspiration and NPP

Nutrients limiting ability

• Terrestrial: soil fertility can account for some variation in terrestrial fertility, particularly due to the limiting amounts of N and P

• Aquatic: light is NOT the primary limiting factor for NPP, but rather nutrients.

  • eg. Phytoplankton biomass controlled by P concentration in lakes, in ocean N

Secondary production

the biomass created by consumer organisms (heterotrophs) by consuming other organisms

Detritus pathway

a food chain that begins with dead organic matter (detritus), which is broken down by decomposers like bacteria and fungi. This decomposition process is followed by detritivores (like earthworms and snails) that consume the detritus and decomposers, which are then consumed by predators, completing the flow of energy and nutrients through the ecosystem

Trophic efficiency

= (net productivity at trophic level i + 1)/ (net productivity at trophic level i)

Nutrients

chemical forms of elements used for the growth of all organisms

Chemical forms of N

NO2, NO3, NH4, N2, etc

How can nitrogen forms that are not usable to plants and animals be pumped into the environment

Cycling- plants that fix nitrogen and animals that dispense nitrogen

Where do nutrients used by autotrophs come from

Outside the ecosystem

• Through the atmosphere

• Earth’s crust

• deep ocean

Within the ecosystem

• recycling consumers/decomposers

Detrital food chain

detritus going to microbes, microbes eaten by microbivores/detrivores, which are in turn consumed by invertebrates

Factors that affect the rate of decomp

temperature ex) understory detritus in Panama decomposing quicker than in montreal

Reservoir

the amount of a specific material in a certain environment

• eg. the amount of N in the atmosphere

Fluxes

the movement of one reservoir to another, measured in units time

Steady state

reservoir size constant and input = output

Mean residence time

mass of material in reservoir/input or output

Non steady state

Reservoir size changes , input or output is greater

Nitrogen fixation

Adds N to the biosphere

Denitrification

Removes N from the atmosphere

2 major reservoirs of N

Atmosphere and Rocks, biosphere cont. much less N than the nature biomes

Oxygen depletion in the aquatic ecosystem (draw)

Carbon cycle greatly affected

by human activity, reservoirs in sedimentary rocks and kerogen

Greenhouse effect

“blanket effect” that warms the earth

source

Adds a gas to the atmosphere, Rtotal/GPP>1

sink

removes a gas from the atmosphere, Rtotal/GPP <1

Net ecosystem production

NEP= GPP- Rtotal

Population ecology

One to two species and how they interact

Community ecology

3 + species, evaluating the value of biodiversity

community

group of all the different living organisms that live and interact in a specific area, typically only the biotic factors

succession

the process of change in ecological communities over time

dispersal & probability of arrival

closer plants will grow

Space-for-time replacement

Looking around at patches of a community that have been more recently disturbed to get a better idea of succession

Primary succession

All biotic factors wiped out. eg. volcano

Factors which affect the rate of primary succession

• soil nutrients, precipitation, spread of disaster, faciliation, availability of colonizers

• the abiotic environment: nutrient availability soil formation

  • processes among the initial species can help or hinder primary succession

typical order of succession

• shorter shrubs or grasses that need sunlight

• quicker growing plants that spread seeds more quickly - those that can float through the air 

forensic entomology

Forensic entomologists focus on the types of insects that colonize a dead body, the order in which they appear, and how their life cycles progress over time. can be used to determine time of death among other factors

absolute density

The number of individuals per unit area or per unit volume.

big-bang reproduction

Offspring are produced in one burst rather than in a repeated manner.

deme

A population genetic unit of individuals that breed with one another; a genetic population.

emigration

The movement of individuals out of an area occupied by the population

immigration

The movement of individuals into an area occupied by the population.

intrinsic capacity for increase

The potential rate of increase of a population that combines the life table and

fertility schedule with the speed of development.

life table

The age-specific mortality schedule of a population.

mean length of a generation

The average length of time between the birth of a female and her offspring.

reproductive rate (R0)

The average number of offspring produced per female or reproductive unit.

reproductive value

The contribution an individual female will make to the future population.

Interspecific competition fitness effect

It reduces the fitness of both competing species.

Adaptation response to interspecific competition

Adaptation should reduce competition by favoring traits that minimize niche overlap.

Niche overlap effect

Larger niche overlap increases competition intensity.

Character displacement definition

Evolutionary divergence of traits between competing species when they co-occur to reduce competition.

Classic example of character displacement

Darwin’s finches on the Galápagos Islands.

Trait involved in finch competition

Beak size/depth determines seed size consumed and drives competitive differences.

Beak size pattern in coexistence

Coexisting finch species show greater beak size divergence than isolated species.

Why character displacement occurs in finches

Natural selection favors traits that reduce niche overlap and competition.

Heritability of finch beak size

Beak size is heritable; offspring resemble parents enabling natural selection.

Predation definition

A process in which one species ingests part or all of another species.

Four forms of predation

Cannibalism

Why herbivory and parasitism count as predation

They involve consumption of tissue or resources from another organism.

Predation effect on prey distribution

Predation shrinks the prey realized niche relative to its fundamental niche.

Predation effect on prey abundance

Predation may or may not reduce prey abundance depending on ecology.

Predation effect on community structure

Predation shapes which species persist and influences food webs.

Keystone predator definition

A predator with a disproportionate influence on community structure.

Predators competing with each other

Predators can compete via exploitation of shared prey.

Organisms suitable for discrete generation models

Many insects

C in discrete predator–prey model

Predator efficiency: fraction of predator–prey encounters that kill prey.

Q in discrete predator–prey model

Conversion efficiency: effectiveness of converting prey consumption into predator offspring.

Prediction of simple discrete model

Predator–prey cycles where predator peaks lag behind prey peaks.

Cycle determinants in discrete model

β

Possible dynamics in discrete model

Stable cycles

Isocline definition

A curve on which population growth for a species is zero.

Prey isocline shape

Hump-shaped due to predation on the left and intraspecific competition on the right.

Prey above their isocline

Prey population decreases.

Prey below their isocline

Prey population increases.

Predator isocline definition

Prey density required for predator growth rate to be zero.

Predators above their isocline

Predator population increases.

Predators below their isocline

Predator population decreases due to insufficient prey.

Effect of predator efficiency on isocline

Efficient predators shift the isocline left; inefficient predators shift it right.

Stable equilibrium condition

Occurs when predator isocline intersects the declining right side of the prey isocline.