lecture - basic ecology

7/31/2019 Lecture - Basic Ecology

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An Introduction to Ecology andThe Biosphere



I. Scope of ecologyA. Interactions between organisms and their

environment

1. Ecology is the scientific study of the interactions betweenorganisms and their environment.

a. Interactions determine distribution and abundance of

organisms.

b. Two main themes in ecology are:- Where do organisms live? & Why?- How many organisms are present? & Why?



Habitat

• The place in which an

organism lives – provides the kinds of food and

shelter, the temperature, and the

amount of moisture the organism

needs to survive



c. Ecology was historically an observational science, often

descriptive natural history.

d. An organism’s environment has both abiotic and biotic

components.

- Abiotic components are nonliving chemical and physicalfactors such as temperature, light, water, and nutrients.

- Biotic components are living factors such as other

organisms.



2. Ecology and evolutionary biology are closely relatedsciences

a. Events that occur in the framework of ecological time(minutes, days, years) translate into effects over evolutionarytime (decades, millennia).

Example: Hawks feeding on mice impact mouse populationand may eventually lead to selection for mice with fur ascamouflage.



3. Ecological research scale ranges from individuals to thebiosphere

a. Organismal ecology is concerned about the way in whichan individual interacts with its environment.

b. Population ecology is the study of a group of individuals

of the same species.

c. Community ecology deals with all interacting specieswithin a particular area.



d. An ecosystem consists of all abiotic factors plus allorganisms that exist in a certain area Ecosystem ecology.

Landscape ecology- interactions among ecosystems.

e. The biosphere is the global ecosystem. Global climate

research is an example of ecology at the biosphere scale.



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1st Level of Organization

• Organism:An individualliving thing that is

made of cells,uses energy,reproduces,responds, grows,and develops

copyright cmassengale



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2nd Level of Organization

• Population:A group oforganisms, all

of the samespecies, whichinterbreed and

live in the sameplace at thesame time.




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3rd Level of Organization

• BiologicalCommunity:All the

populations ofdifferentspecies that live

in the sameplace at thesame time.




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4th Level of Organization

• Ecosystem: Populations of plantsand animals that

interact with eachother in a given areawith the abiotic

components of thatarea. (terrestrialor aquatic)




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5th Level of Organization

• Biosphere:The portion

of Earththat

supportslife.




II. Factors affecting the distribution of organisms

- Biogeography is the study of past and present distributionof individual species.



A S i di l ib h di ib i f



A. Species dispersal contributes to the distribution oforganisms

Dispersal refers to the process of distribution of

individuals within geographic population boundaries.

Question: Is the distribution of a species limited bydispersal, i.e. by movement of the organisms?

Answer can be obtained by transplant experiments.

If the transplant is successful, then the organisms justhaven’t reached the target area. If the transplant is not successful, then other factorslimit the distribution of the organisms, such ascompetitors, lack of a food source, etc.



a. Introduced species sometimes have disasterous impacts:

- African honeybee, Zebra mussels

Many introductions intentional.

The “Laws of 10”.

Why do the successful invaders succeed?

Invasional meltdowns?

Climate change effects?



B B h i d h bit t l ti t ib t t th



B. Behavior and habitat selection contribute to thedistribution of organisms

1. Organisms may not occupy all potentially suitable

habitat. Why? a. Evolution doesn’t lead to perfect organisms.

b. Evolution is an ongoing process. Environmentschange, but it takes a while for organisms to respond.

C. Biotic factors affect distribution

1. Organisms required for potential community members tocolonize may be lacking.

- Pollinators, prey, predators that limit competition



D. Abiotic factors affect distribution

1. Abiotic factors of interest include:

- Temperature (range from 0 to 45 C)

- Water

- Sunlight

- Wind (increases heat & water loss)

- Rocks and soil



• Local and seasonal effects on climate.

– Bodies of water and topographic features such as

mountain ranges can affect local climates.

– Ocean currents can influence climate in coastal

areas.

– Mountains affect rainfall greatly.

Fig. 50.14

Copyright © 2002 Pearson Education, Inc., publishing as Benjamin Cummings



b. Lake stratification and mixing alters oxygen andnutrient levels. Dependent on temperature changes andeffect on water density.



Biosphere

• The part of Earth that supports life

–

Top portion of Earth's crust – All the waters that cover Earth's

surface

– Atmosphere that surrounds Earth.



Aquatic and terrestrial biomes

(Biome = major ecosystem type)



A. Aquatic biomes cover about 75% of the earth’s surface

- Wetlands

- Lakes

- Rivers, streams

- Intertidal zones

- Oceanic pelagic biome

- Coral reefs

- Benthos



Oligotrophic Lake: Nutrient poor, water is clear,

oxygen rich; little productivity by algae, relativelydeep with little surface area.



Eutrophic lake: nutrientrich, lots of algal

productivity so it’s oxygen

poor at times, water ismurkier often a result ofinput of agriculturalfertilizers



Rivers and Streams: Organisms need adaptationsso that they are not swept away by moving water;

heavily affected by man changing the course offlow (E.g. dams and channel-straightening) and byusing rivers to dispose of waste.



Wetlands: includes marshes, bogs, swamps, seasonal ponds.Among richest biomes with respect to biodiversity and

productivity. Very few now exist as they are thought of often

as wastelands.



Estuary: Place where freshwater stream or river mergeswith the ocean. Highly productive biome; important forfisheries and feeding places for water fowl. Often heavilypolluted from river input so many fisheries are now lost.



Marine environment with zonation.



Intertidal Zone: Alternately

submerged and exposed bydaily cycle of tides. Oftenpolluted by oil that decreasesbiodiversity.



Coral Reefs: occur in neriticzones of warm, tropicalwater, dominated by

cnidarians (corals); veryproductive, protect landfrom storms; most are nowdying from rise in globaltemperatures



Deep-sea vent: Occurs in benthic zone; diverse, unusualorganisms; energy comes not from light but from

chemicals released from the magma.



B. Terrestrial biomes

- Tropical forest

- Savanna

- Desert - Chaparral - Temperate grassland

- Temperate deciduous forest - Coniferous forest - Tundra



Tropical Forest: Vertical stratification with trees incanopy blocking light to bottom strata. Many treescovered by epiphytes (plants that grow on other plants).



Example of Tropical, Dry

Forest



Desert: Sparse rainfall (< 30 cm per year), plants andanimals adapted for water storage and conservation. Can

be either very, very hot, or very cold (e.g. Antarctica)



Chaparral: Dense, spiny, evergreen shrubs, mild rainywinters; long, hot, dry summers. Periodic fires, someplants require fire for seeds to germinate.



Temperate Grassland: Marked by seasonal drought andfires, and grazing by large animals. Rich habitat for

agriculture, very little prairie exists in US today.



Temperate Deciduous Forest: Mid-latitudes with moderateamounts of moisture, distinct vertical strata: trees,

understory shrubs, herbaceous sub-stratum. Loss ofleaves in cold, many animals hibernate or migrate then.Original forests lost from North America by logging andclearing.



Coniferous forest: Largest terrestial biome on earth, oldgrowth forests rapidly disappearing, usually receives lots

of moisture as rain or snow.



Tundra: Permafrost (Permanent frozen ground), bittercold, high winds and thus no trees. Has 20% of landsurface on earth.

lecture - basic ecology

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