Ecology

The study of the interactions between

organisms and their environment

Ecology Part 1

Interdependence

• Living organisms depend on the biotic and abiotic parts of their environment

• Any change in an environment can have far

reaching consequences

Biotic: living organisms in an environment

ex: Plants, animals, bacteria, etc.

Abiotic: physical & chemical (nonliving) parts

ex: Precipitation, soil, temperature

- Not constant, fluctuates

Properties of Populations

Pop. Density: “how crowded”

# individuals / unit area of volume

ex: Human: U.S. = 30/km2 (2006)

China = 135/km2

Japan = 337/km2

Properties (cont'd)

Dispersion: spatial distribution w/in pop. 3 patterns:

1. Clumped – gathered around limited resources - herding/flocking behavior

2. Random – position is independent of others;

rare

3. Uniform – stay as far away from others

as possible

- nesting behavior

Population Dynamics

Birthrate - # births / period of time U.S. ~ 3.9 mill./yr

Deathrate – aka mortality rate - # deaths / period of time U.S. ~2.5 mill./yr

BR > DR = growing population

Dynamics (cont'd)

Life Expectancy: avg. life span

U.S. Males 74, females 80

Survivorship Curve – show probability of

survival to a certain age.

1.

Measuring Populations

Growth Rate - change in pop. size over time

Depends on BR, DR, & migration

Data represented as “per capita” (avg. per

person)

- GR = population ↓

+ GR = population ↑

Population Models

Exponential Model - growth w/o limits Does not apply to most pop. b/c requires

unlimited resources In nature, resources are limited

Limiting Factors

Any factor that restrains pop. growth

2 types:

1. Density Independent: reduces pop. by same proportion regardless of pop. size

– ex: fire or flood

Limiting Factors (cont'd)

2. Density Dependent: chance of surviving or reproducing depends on pop. density

Why? As pop ↑, competition ↑

immunity, growth & reproduction ↓

ex: ↓ food

Logistic Model

Exponential model + limiting factors

Includes carrying capacity (k):

# individuals environment can support over long period of time

Graphically assumes k is constant,

although it actually varies

Logistic Model

Population Fluctuations

Lynx & Hare Famous population study

Charles Elton

hare = lynx

hare = lynx

Ecology Part 2

Habitat vs. Niche

Habitat: place where an organism lives Niche: Habitat + role played in environment

Generalist – broad niche; lives anywhere eats anything

ex: raccoon

Specialist – narrow niche: specific habitat & diet

ex: koala

Competition

• Resources are limited; survival depends on competition

• Intraspecific competition – competition

w/i a population (density dependent) • Interspecific competition – competition

between different species

Competitive Exclusion

2 groups cannot occupy the same niche: Fierce competition results in extinction OR

habitat change

Invasive Species

Non-native species introduced to an

ecosystem

Compete with native species

Negatively impact carrying capacity

Kudzu

Asian

Carp

Zebra

Mussels

Patterns in Communities

Species Richness

• # unique species in a community

• Varies w/ distance from equator

– Closer to equator = ↑ species richness

Species Eveness

• Relative abundance of each species

• How common a species is

Succession

• Gradual, sequential growth or regrowth of a community

• 2 types:

1. Primary Succession

2. Secondary Succession

• Pioneer species: 1st tiny plants “hardy” species

Primary Succession

• Development of life in an area that has not supported life before.

Secondary Succession

• Sequential replacement of species following the disruption of an existing community

• Climax community: fully regrown, all animal life has returned

Ecology Part 3

Environmental Issues

Air Pollution

• Smog = smoke + fog

• Effects of air pollution:

1. ozone thinning

2. global warming

3. acid precipitation

Ozone Thinning

• Chlorofluorocarbons (cfcs)

– Found in coolants, propellants, plastics,

& foam

– 1 cfc molecule destroys 100K ozone (O3)

molec.

– If O3 ↓10% = 300,000 new cancer cases

Global Warming

• ↑ CO2 = ↑ greenhouse effect = ↑ temp

• Too much solar energy trapped

• Avg. temps ↑1.01ºF in last 100 yrs.

• Estimate: temps will ↑ 4ºF in next 100 yrs.

• Affects rainfall patterns, soil moisture, sea

level

• Human role in global warming:

–Concentration of CO2 has increased 30% in

past 30 years

–d/t burning fossil fuels (coal, oil, natural gas)

–d/t destruction of vegetation: less plants to absorb CO2

Acid Precipitation

• Air pollution + water vapor = acid rain

• normal pH

• Effects: disease or death in plants &

animals

Water Pollution

• Sewage, industrial waste, agricultural runoff

• Affects living organisms

Biological magnification

– Chemical enters ecosystem

– Concentration ↑ as it moves up food

chain b/c builds up & remains in tissues

Biodiversity

Variety of life forms

2 types:

Species diversity – depends on species richness & evenness

Genetic diversity – diversity of alleles

• ↑ diversity = ↑ ability to survive

• ↓ diversity = ↓ ability to survive

Ecosystem Disruption

• Destruction or major change in ecosystem • Endangers life, causes extinction Keystone Species:

–Species critical to functioning of ecosystem

ex: sea otter:← s. urchins ← kelp

if sea otters ↓ (hunted), ↑ urchins, ↓↓ kelp

Sustainability

• Ability of Earth to meet needs of humans so

that population can exist forever

• To ↑ sustainability:

–Energy conservation

–Slow or ↓ human pop. growth

– ↓consumption of natural resources

Environmental Solutions

• Conservation Biology –Seeks to ID, & protect areas rich in

biodiversity • Restoration Biology

–Deals w/ extreme ecosystem damage –Habitat remediation

What Can Science Do?

• Study bioindicators- species very sensitive

to ecological change

•Early warning of problems

•ex: Diporeia

Protect biodiversity hotspots

regions richest in unique but threatened

species - 25 worldwide