Ecosystems and Populations

Terms Ecology: study of

how organisms interact with each other and their non-living environment (biotic-living and abiotic-non living factors)

Ecosystem: The biotic community and all abiotic factors.

Community: All the living organisms/populations in an area

Population: group of organisms of same species

Roles in Ecosystems Habitat: the area

where an organism lives; its address (eg. Tropical rainforest);

Niche: an organism’s profession; what it eats, what eats it, the habitat, time when active, etc.

Competition Having differing niches

allows organisms to reduce competition

Eg. Hawks vs. owls

Competition

Warblers Yellow rumped – only in bottoms of trees

Blackburnian – only at tops of trees

Biodiversity

describes the number and variety of organisms in an ecosystem.

Greater biodiversity means more stability because if one species in a food web is lost, its predator can switch to another prey.

Indicator Species are species of organisms that provide an

early warning that an ecosystem is being affected by some factor.

Usually, these species are very sensitive to changes in an ecosystem, or to specific changes of ecosystem conditions.

Exotic Species Second only to

habitat loss as a cause of extinction

New species occupy niches of natural populations and out compete them

purple loosestrife

zebra mussels

starlings

Special concern – numbers are declining at the range / fringe of the area

Threatened – species may become endangered if threatening conditions are not reversed

Extirpated – a species no longer exists in one particular area, but is still found in other areas

Endangered – a species is close to extinction in all parts of their natural habitat

Extinct – a species no longer exists

Less severe risk

Most severe risk

Species At Risk

Extinct Canadian SpeciesGreat Auk -1844

Sea Mink-1870

Labrador duck-1875

Genetically Modified Crops

Transfer of genes from one organism to another unrelated organism

Eg. Roundup resistance to canola

Fish antifreeze proteins to strawberries

Vitamin A gene to rice

Green Fluorescent

Protein to monkeys/pigs

Biological Control

Using a natural predator to control an unwanted species.

Population Line Graphs

typically have numbers on vertical axis and time on horizontal axis

Biotic Potential

the maximum number of offspring that the species could produce with unlimited resources

Environmental Resistance

Is the limiting factors on a population

Include food, shelter, water, predation, etc.

Puts brakes on biotic potential (B) – maximum reproductive rate

Logistic Growth

S shaped curves are typical of stable populations with a constant food source

Logistic Growth

Eg. Wild Horses on reserve land in AB

Exponential Growth

J shaped curve (initially) occurs with short-lived populations that rapidly deplete their environment

Exponential Growth

Eg. Flies on a carcass

Carrying Capacity

Is the number of organisms a habitat can sustain over the long term

“k”

Overshoots

Result when k is greatly exceeded and the environment deteriorates

Limiting Factors to Populations

Shelford’s Law of Tolerance: an organism can survive within a certain range of any abiotic factor

Greater the range, the greater the ability for the species to survive

Limiting Factors on Populations

Law of the Minimum: if any one of many needed nutrients/limiting factors is reduced below the required levels, the population growth rate declines

Limiting Factors

Can be density independent – those that will affect a population regardless of its size Eg. Cold winter

Lack of water

Limiting Factors

Can be density dependant – those that increase when the population size increases Eg. Disease

Predation Food Supply

Human Population Growth

Approximately 6.6 billion

Taxonomy - naming

Naming system to identify different species

Used binomial nomenclature – two words

Taxonomy

First word is the genus Second is the species

Equus caballus

Equus burchellii

Taxonomy

Castor canadensis Ursus maritimus

Species - Definition

A species is a group of organisms that can interbreed under natural conditions and produce fertile offspring

Levels of Classification

Kingdom AnimaliaPhylum ChordataClass MammaliaOrder PrimatesFamily HominidaeGenus HomoSpecies sapiens

(Kings play chess on fine grain sand)

Classification Giraffe Horse Pig

Kingdom Animalia Animalia Animalia

Phylum Chordata Chordata Chordata

Class Mammalia Mammalia Mammalia

Order Artiodactyla Perissodactyla Artiodactyla

Family Giraffidae Equidae Suidae

Genus Giraffa Equus Sus

Species camelopardalis caballus scrofa

The Kingdoms

5 of them:

1. Monera: Bacteria and blue-green algae

- sometimes subdivided into eubacteria and archaebacteria

- prokaryotic (very simple) cells

2. Protista – mostly single celled

- Eukaryotic (true nucleus)

- Usually aquatic

3. Fungi – most multicellular

- Heterotrophic, chitin cell walls

4. Plantae: multicellular, autotrophs

5. Animalia: multicellular, heterotrophs