Ecosystems and Living Organisms

Chapter 4

Evolution

• Genetic changes in a population through time.

• Occurs through natural selection

Overproduction

Variation

Struggle for existence

Differential reproductive success

Evolution

Darwin’s Finches

Evolution

Kingdoms of Life

Biological Communities

Rotting Log Community

Biological Communities

Succession:

How Communities Change over Time

Primary succession –

Lichens

Mosses

Rocks

Biological Communities

Succession: How Communities Change over Time

Primary succession –Rocks

Lichens

Mosses

Grasses

Shrubs

Biological Communities

Succession: How Communities Change over Time

Primary succession –Rocks

Lichens

Mosses

Grasses

Shrubs

Trees

Biological Communities

Secondary Succession

Interactions Among Organisms

Symbiosis –

• one species living in or on another species

• results from coevolution

Interactions Among Organisms

Symbiosis –

Three types

1) Mutualism

Without mycorrhizae With mycorrhizae

Interactions Among Organisms

Symbiosis –

Three types

2) Commensalism

Epiphytes

Interactions Among Organisms

Symbiosis –

Three types

3) Parasitism

Tracheal mites

Interactions Among Organisms

Predation – predators consuming prey

Most common method:Pursuit and Ambush

Interactions Among Organisms

Animals that consume plants = herbivores

Animals that consume animals = carnivores

(can be further subdivided based on prey type, such as an insectivore)

Interactions Among Organisms

Defenses against predators:

Plant defenses –

• spines, thorns

• leathery leaves

• toxic chemicals

• thick waxes

Interactions Among Organisms

Defenses against predators:

Animal defenses –

• armor, spines• toxic chemicals

Interactions Among Organisms

Defenses against predators:

Animal defenses –

• armor, spines• toxic chemicals

• camouflage

• running away

Interactions Among Organisms

Competition –

individuals attempting to utilize common resources

• Intraspecific competition

• Interspecific competition

The Ecological Niche

• An organism’s adaptations, use of resources, lifestyle, and habitat.

Fundamental vs. Realized Niche

Example: Tale of Two Anoles

Green Anole Brown Anole

The Ecological Niche

Fundamental vs. Realized Niche

Fundamental Niche of Green Anole

Fundamental Niche of Brown Anole

Ove

rlap

Brown anole out-competes green anole, therefore . . .

The Ecological Niche

Fundamental vs. Realized Niche

Realized Niche of Green Anole

Ove

rlap Realized

Niche of Brown Anole

The Ecological Niche

Limiting Resources

The Ecological Niche

Competitive Exclusion

The Ecological Niche

Competitive Exclusion

The Ecological Niche

Competitive Exclusion

The Ecological Niche

Resource partitioning

Keystone Species

• Single species that strongly influences an entire community.

• Example: figs

- frugivores depend upon fruit

- usually avoid figs, but during certain times of the year, figs are only species bearing fruit

- if figs were eliminated, many frugivores would die out

Species Richness

Number of different species in a community

Species Richness

Forest Grassland

EC

OT

ON

E

Where edge effect occurs

Typically greater species richness

Species Richness

Species Richness and Ecosystem Services

Ecosystem Ecosystem services

Forests,Grasslands

Purify air / waterProduce / maintain soilAbsorb CO2

Wildlife habitat

Freshwater systems

Moderate water flowMitigate floodingDilute / remove pollutantsDrinking water

Recreation

Species Richness

Species Richness and Community Stability

Greater the richness = Greater the stability