Biological Communities & Biological Communities & Species InteractionSpecies Interaction

Who Lives Where and Why?

Critical Factors and Tolerance Limits1. nutrients, temperature, water supply, living

space and other physical factors

2. tolerance limits - minimum and maximum levels (range) for each of the critical factors

3. factors are unique for each species, and often complex interaction between several factors

Saguaro cacti are extremelySensitive to temperature

Desert pupfish, lives in desert, Can survive at high temp up to42 C and in high salt.But eggs and juvenile fish live between 20-36C and are killed by high salt

Environmental Indicators

Jimson Weed a.k.a Loco Weed, or Devil’s Weed

Grows where selenium and uranium are high

Datura stramonium

Lichen and Frogs are Pollution Indicators

Mulefat: native plant, indicates the presence of water

Natural Selection, Adaptation, Evolution1. physiological modifications - traits of species

that allow them to “adapt” to environment

2. evolution by natural selection -over time, traits that are beneficial “survive” while those that are less beneficial do not

3. factors influencing evolution - change in environment; predation; competition; luck

A trait that provides and advantage is known as an ADAPTATION

Selection (Natural or Artificial)

The Ecological Niche1. habitat -place and environmental conditions in

which an organism lives

2. ecological niche - functional description of role of species within a community

how it obtains food relationships with other species role it plays in biotic and abiotic aspects of area

Predation1. predator -an organism that feeds directly on

another living organism predator - prey relationships play vital a central role

in evolution of many species competitive exclusion principle - two species whose

niche overlap too much will compete for resources

                                                                                                                              

                                                                                                                                                      

                                                                                                                                                                          

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KEYSTONE SPECIE

Keystone Species1. keystone species - species or group of species

whose impact on community is greatest not always the highest on the food chain

i.e. Wolves limit the grazing of herbivores

i.e. Sea star limits population of clams etc.

Parasite: A type of symbiosis in which organism that completes part of its life cycle on a host organism. The host is harmed and the predator is not.

Pathogen: Disease causing organisms that are not free living.

Competition1. intraspecific competition - competition for

resources among members of same species territoriality

2. interspecific competion - competition for resources among members of different species

What two ways do grasses compete?Why is intraspecific competiton more intense?

Symbiosis - intimate interaction of species (often with one relying on another)

1. commensalism- one organism benefits, other is neither helped nor harmed

i.e. Bird in a tree

2. mutualism -both organisms benefit from a mutual relationship with each other

i.e. mycorrhizae and lichen

3. parasites- one organism benefits one is harmed

i.e. Sporozoan that causes malaria

Mimicry and Camouflage

1. Batesian mimicry- a related species evolves over time to appear similar to a dangerous species

Butterflies

Left is unpalatable

Right is palatable

Batesian Mimicry

2. Muellerian mimicry - one species evolves over time to appear similar to unrelated species

Camouflage

Community Properties

Productivity - rate of biomass production Abundance and Diversity

1. abundance - actual total number of individual organisms in a community

2. diversity - number of actual species or niches present in a particular ecosystem

What Is…..?

ZooPlankton Phytoplankton Giant Kelp

Complexity and Connectedness1. complexity - number of species at each trophic

level and number of trophic levels

2. connectedness - the relatedness of organisms within the entire trophic system

Resilience and Stability– constancy - lack of much change over time– inertia - change occurs, much resistance– renewal - ability to repair after severe damage

Community Structure– spatial distribution of organisms– relation of organisms to their surroundings

nesting birds schools of fish clusters of trees

Factors influencing distribution

Dispersal methods a) availability of water in the desert Behavior Biotic factors (predation parasitism, competition,

disease) b) competition for nesting space in a penguin

colony. c) clustered (optimum protection bird and fish) Abiotic factors (availability of nutrients, water,

light or presence of chemicals)

Community in Transition

Ecological Succession - gradual change of ecosystem over time1. primary succesion - community develops on

site with little/no biotic forms

2. secondary succession - new species begin to replace “original” species on the site

3. climax community - community that finally develops and resists any further change

4. equlibrium community - undergoes periodic disruptions and renewal

forests, grasslands

5. fire-climax community - often depends upon fire for part of it normal life cycle

the chaparral

Introduced Species - new species brought into a community1. natural -species moves into a community

without human intervention2. human introductions - new species brought

into community by humans eucalyptus trees Rabbits in Australia Mongoose in Jamaica and Hawaii

Mongoose fighting Cobra

Overgrowth of Introduced RabbitsIn Australia