Lecture 4

Ecosystems & Living

OrganismsLecture 4

Ecosystems & Living Organisms

Ecosystems & Living Organisms

There are 3 main interactions among organisms:

1. Predation

2. Symbiosis

3. Competition

Predation- relationship where one organism

consumes another

- includes both animals eating other animals and animals eating plants.

Predator

- depends totally or in part on killing another organism for its food

Prey

- organism killed and eaten by a predator

Predator Strategies

Predator strategies include:

1. Pursuit (chase)

2. Ambush (lie in wait)

3. Special hunting traits e.g., speed, agility, claws

4. Traps

5. Hunting in packs

Prey Strategies

Plant Defense Strategies include:

- spines or thorns

- leathery or waxy leaves

- produce bitter or poisonous chemicals

Prey Strategies

Animal Defense Strategies include:

- fleeing

- camouflage

- mechanical defenses, e.g., horns, quills

- group living

- warning coloration

Symbiosis

- a close relationship between 2 or more unrelated species

The 3 main types of symbiotic relationships:

1. Mutualism

2. Commensalism

3. Parasitism

Mutualism- symbiotic relationship where both organisms benefit from each other

shark

remora

- symbiotic relationship where both organisms benefit from each other

MUTUALISM – Clownfish and Sea anemone

Commensalism

- symbiotic relationship where one organism benefits while the other is unaffected

COMMENSALISM - Barnacles encrusted on

surface of whale

Parasitism

- symbiotic relationship where one organism (HOST) is adversely affected by another which benefits (PARASITE)

- well-adapted parasites do not kill their host

- e.g., tick on dog, tapeworm in human gut

                                                                                                                           

PARASITISM – Tapeworm in human

Hooks and suckers on head for attachment to

body organs

PARASITISM − Tomato Hornworm covered with cocoon of braconid wasps

Ecological Niche

Niche

- the sum total of all the requirements and activities of a species

- an organism’s unique role

- an organism’s “profession”

- reduces competition between species

Fundamental vs. Realized Niche

Fundamental Niche

- full potential range of physical, chemical & biological factors a species could use if there were no competition from other species

Fundamental vs. Realized Niche

Realized Niche

- the portion of the fundamental niche that a species actually occupies

- species with a narrow realized niche (specialist species) are more susceptible to extinction

Habitat

- the physical & biological resources required by an organism

- an organism’s “address”

Competition

- if 2 different species require a common resource they are said to be in competition for it

Competitive Exclusion Principle

- also called Gause’s Principle

- 2 species cannot live in the same identical niche & if they try 1 will be excluded

Evolution & Succession

Evolution & SuccessionEvolution

- change in the genetic material of a population of organisms from one generation to the next.

- involve processes which introduce new variations / characteristics (mutations or interbreeding) and processes that make new variants either increasingly rare or common.

- does not necessarily mean speciation

Natural Selection

- a theory advanced by Charles Darwin (1809 – 1882) to explain how evolutionary change occurs

- if certain individuals are better able to survive & leave more offspring because of their genetic traits, then frequency of the genes will change over subsequent generations

Succession

• Succession is a process of community development that involves a changing sequence of species.

Succession• The pioneer community is the first community to colonise

or re-colonise an area.

• Primary succession is community development in an area that has not been previously inhabited e.g. on bare rock, sand, hardened lava flow from volcano, area left by a retreating glacier.

• Secondary succession is community development in an environment that has been previously inhabited but was destroyed by some process e.g. fire, flood, harvesting etc.

Primary Succession on a lava field on the Rangitoto Island near New Zealand.

http://en.wikipedia.org/wiki/File:Rangitotolavapath.jpg

Usually takes thousands of years to reach climax community

Secondary Succession

Secondary Succession on an uncultivated fieldhttp://en.wikipedia.org/wiki/File:Secondary_succesion_cm01.jpg

Usually takes hundreds of years to reach climax community

Biomes & Biodiversity

Biomes

- large relatively distinct terrestrial regions

- characterized by similar climate, soil, plants and animals regardless of where they occur in the world

Biomes cont’dThe 9 major biomes are:

• tropical rain forest• savannah

• desert• chaparral

• temperate grassland• temperate deciduous forest

• temperate rain forest• taiga

• tundra

Biomes cont’d

- precipitation and temperature are the most important factors

determining the type of desert, grassland, or forest

- climate and vegetation both vary with latitude and altitude

Weather & Climate

Weather

- short-term changes in temperature, pressure, precipitation and other conditions in the atmosphere at a given place & time

Weather & Climate cont’d

Climate

- average weather of an area

- taken over a period of at least 30 years

- temperature & precipitation are the 2 most important factors that determine climate

BiomesBIOMES OF THE WORLD

BIOMES OF THE WORLDhttp://www.marietta.edu/~biol/biomes/

biome.jpg

TUNDRA

http://en.wikipedia.org/wiki/File:800px-Map-Tundra.png

Tundra

- also called arctic tundra

- just south of the arctic polar ice cap

- covered with ice & snow

- bitterly cold

- permafrost

TUNDRA

TUNDRAhttp://en.wikipedia.org/wiki/File:Greenland_scoresby-

sydkapp2_hg.jpg

TUNDRAhttp://en.wikipedia.org/wiki/File:Kerguelen_RallierDuBatty.JPG

TAIGA

http://en.wikipedia.org/wiki/File:Distribution_Taiga.png

Taiga

- also called swamp forest or boreal forest

- south of the arctic tundra

- long, cold, dry winters with 6-8 hrs sunlight

- dominated by few species of coniferous evergreens

TAIGATAIGAhttp://en.wikipedia.org/wiki/File:Picea_glauca_taiga.jpg

TROPICAL RAIN FORESTSwww.marietta.edu/~biol/biomes/

Tropical Rain Forest

- found near equator- warm temperature- high precipitation - thin, nutrient-poor soil- high biological diversity- being lost to slash-and-

burn cultivation and for collection of lumber.

SUBTROPICAL DESERTShttp://www.marietta.edu/~biol/biomes/images/desert/desert_500.jpg

Deserts

- precipitation <10 inches per year

- widely-spaced low vegetation

- slow plant growth rate

- low species diversity

http://test.scoilnet.ie/res/crosswords/desert.jpg

DESERT

DESERT