evr lecture 9-12

Ecosystem

a biological community of interacting organisms and their physical environment

Ecosystem chemical cycling

For complete recycling of chemical elements, several species must interact (need more than one species to have ecosystem)

Simply a community will have (never that simple)

Producer

Decomposer

Fluid medium

Ecological communities

Set of interacting species found in the same place and functioning to maintain life

Species

group of living organisms consisting of similar indivudauls capable of exchanging genes or interbreeding

Population

a group of organisms of one species that interbreed and live in the same place at the same time

Trophic level

number of feeding levels away from original source of energy

First trophic level

base, primary producers

Second trophic level:

primary consumers, herbivores, heterotrophs (feeds on other organisms)

Third trophic level:

feeds directly on herbivores, secondary consumer

Fourth trophic level:

Feeds on third-level carnivores, territory consumer

Decomposers:

feed on waste and dead no matter what level, crucial!!

Ecosystem energy flow

movement of energy through an ecosystem from the external environment through a series of organisms and back to external environment

Biomass

the total amount of organic matter on earth or in any ecosystem or rea

Measured as the amount the amount per unit surface area

Biological production

Capture of usable energy from the environment to produce organic compounds

Primary production

Autotrophs (and checmo autotrophs)

Photosynthesis or chemosynthesis

Competition

Interactions among organisms that compete for limited, shared resources

Intraspecific competition

Members of the same species pursue shared resources

Interspecific competitions

organism from different species also compete for shared resources

interspecific competition

If you remove a competitor the remaining species will have greater access to resources → remaining species will thus grow faster

Competitive exclusion principle

two species that directly compete for essential resources cannot coexist

Fundamental (or theoretical) niche

the complete range of environmental conditions (temp, food, water) over which the species might possibly exist

Realized niche

range of conditions over which a species actually occurs

Niche differentiation

potential competitors are able to coexist because they divide up the fundamental niche

Exploitation competition

competition for shared resource

Ex: One species of desert plant taking up all the water

Interference competition

aggressive actions designed to drive off a competitor

Scavengers like hyenas or vultures

Plants can as well by releasing chemicals that inhibit others plants

Ecological Interactions

Herbivory, Predation, Parasitms

Grazers

feed directly on the leaves and young stems of plants

Feeding challenges associated with chemical nature of food

Leaves and stems are formed of cellulose (glucose polymer) that is resistant to breakdown

Prey switching

many predators feed on multiple prey and they can switch to a new prey if one becomes depleted

Ecological Interactions

Mutualism and Commensalism

Symbioses

intimate interdependencies between species

Mutualism

Both organisms benefit

Commensalism

one species benefits, other is unaffected

Primary succession (completely new)

Establishment and development of an ecosystem where one did not previously exist

Ex: Lava flow and creating Hawaiian island

Secondary Succesion

Reestablishment of an ecosystem following disturbance

Remnants of previous biological community (soil, seeds, organic material,etc)

Ex: Forests that develop on abandoned pastures

In addition to exchanging symbionts, corals have a few other mechanism for dealing with changing light

Changing tentancle extension

Reduced density of cells and pigments, to increase or reduce self shading

Enzyme adaptions

Excitation pathways that convert light to utizable wavelengths

symbiosis

A close relationship between two species that benefits at least one of the species.

past threats to FL reefs were:

Nutrient run offs

Mangrove forests used to filter them before they were removed

Pollution: 33 tons of pollutants are discharged from islands each year

Biodiversity:

The variety of life in a particular habitat or ecosystem

Genetic diversity

total number of genetic characteristics of specific species, subspecies, or group of species

Species richness

total number of species

Species evenness

relative abundance of each species

Species dominance

the most abundant species

Genotype

the genetic makeup of a cell, an organism, or an individual

Phenotype

the outward appearance of an organism; the expression of a genotype in the form of traits that can be seen and measured

Ex hair or eye color or disease resistance

Species diversity

The number (or evenness) of species within an ecosystem or on the entire planet

Functional redundancy

species that fill similar niches can replace each other if on goes extinct

Four processes lead to evolution

Mutation

Natural selection

Allopatric speciation

Adaptive radiation

Allopatric speciation

two populations become geographically isolated for a long time

Differences accumulate so that they no longer reproduce with each other

Two new species have formed

Adaptive radiation

organisms diversity rapidly into a multitude of new forms, particularly when a change in the environment makes new resources available, creates new challenges, and opens environmental niches

Genetic Drift

Changes in frequency of a gene in a population simply by change

Founder effect

Small number of individuals are isolated from a larger population

Divergent evolution

population is divided and each evolves separately

ex. Polar and brown bear

Convergent evolution

given sufficient time and similar climates species similar in shape and form will tend to appear

Factors that tend to increase diversity

-A physically diverse habitat

-Moderate amounts of disturbance

-A small variation in environmental conditions

-High diversity at one trophic level increases the diversity at another tropic level

-An environment highly modified by life

-Middle stages of succession

Factors that tend to decrease diversity

-Environmental stress

-Extreme enviornments

-A severe limitation in the supply of an essential resource

-Extreme amounts of disturbance

-Recent introduction of exotic species

-Geographic isolation

Biomes

Similar environments provide similar opportunities and similar constraints

Species diversity tends to decrease from..

the tropics to the poles

Tropical forests and tropical coral reefs are some of the worlds most diverse habitat

Biodiversity hotspots

places that have an unusually large number of endemic species

Endemic species

a species that is unique to a defined geographic location (not found anywhere else)

People alter biodiversity by:

-Direct hunting

-Directly disturbing habitats

-Introducing exoctic species into new habitats