The Biosphere

Earth: A Living Planet

General Vocabulary

Ecology: The study of how living organisms interact with each other and with their surroundings.

Biosphere: Part of the Earth in which life exists (water, land, air)

Ecosystem: Area defined by its abiotic and biotic traits– All ecosystems overlap with neighboring

ecosystems ex. forest and a pond found within the forest

Traits of an ecosystem

Abiotic Soil type Amount of sunshine Amount of rain Rock types Temperature

Biotic Plants:

– Trees– Shrubs– Grasses– Fungi

Animals:– Rodents– Insects– Large animals

Succession

Changes in an ecosystem where one type of organism replaces another over 100’s of years.

Pioneer Species: colonizes an area for the first time (ex. first plants to grow after a volcanic eruption)

Climax community: “end point” – organisms found in a climax community do not continue to change – they are very stable

Energy and Nutrients

Flow of Energy

Plants convert sunlight into usable energy for animals (photosynthesis)

After energy is used by an organism, it cannot be re-used…energy FLOWS it does not CYCLE!

Trophic (feeding) Levels

Producer: (photosynthetic plants) – uses sunlight to make its own food

Consumer: organism that gets energy from a producer– Primary, secondary, tertiary…

Decomposer: live on non-living organisms

10% Rule

At each trophic level, only 10% of the energy that is consumed is available to the next trophic level

WHY?– Because most of what the animal eats is

used by the animal (doing life processes… running, hiding, eating, breathing etc… all of this uses energy!)

Ecological Pyramid

Producers

Primary Consumers

Secondary Consumers

Tertiary Consumers

At each level: biomass, numbers and energy are reduced

Food Webs

Ecological pyramid demonstrates a single food chain…

Food Chain: sequence of organisms that eat one another BUT

Food chain is oversimplified. Weaving food chains together is called a food web and reflects true relationships within an ecosystem

Nutrient Cycles

Because nutrients are used and re-used, they form cycles

Nutrients in soil used by plants

Animal eats plants and uses nutrients

Animal eats animals and uses nutrients

Animal dies & decomposes Nutrients returned to soil

Nutrient Cycles

Limiting Factor: a nutrient that is found in small amounts and limits the growth of a population– Ex. Nitrogen usually limits algae growth in

ponds. By adding more nitrogen, algae no longer has limited growth and results in algae blooms… leads to fish death

Populations and Communities

Population Growth

Population: group of the same species that live in the same area in a given time.

If living conditions are IDEAL, growth will be exponential… there is nothing to inhibit growth!

In reality – exponential growth is not sustainable – there will always be a limiting factor– Can you think of an exception to this??

Logistic Growth

Real growth curves will eventually reach a steady state = the carrying capacity of the environment for that species

A population cannot continue to grow forever because of:– Lack of food– Overcrowding (lack of space)– Competition within the population

Factors that control population growth

Density-Dependent

Limiting Factors: Factors that affect

large and/or overcrowded populations

Density-Independent Limiting Factors:

Weather and natural occurrences that have nothing to do with the density of a population

Density-Dependent Limiting Factors

1. Competition (for food, space, water, sunlight…)

Remember: if two species compete for the same niche, one will lose. Natural selection allows for both species to survive if one species evolves and adapts to a different niche

Density-Dependent Limiting Factors

2. Predation Predator-prey relationships keep both

populations in balance As prey pop. increases… the predator pop. will

increase… as predator pop. increases, prey pop. will decrease… as prey pop. decreases, predator pop. will decrease… this allows prey pop. to increase… and the cycle begins again

Density-Dependent Limiting Factors

3. Parasitism Parasites: live off host organism without killing it Thrive best in large, stressed populations

(stressed populations are susceptible to disease)

More easily spread in overcrowded populations

Density-Dependent Limiting Factors

4. Crowding and Stress Smaller area per animal in which to find home

and/or hunt for food Crowded populations tend to fight

Interactions within and between Communities

Community: all the populations that live together within an area. – They live together – therefore they interact

Interactions include:– Competition– Predator/prey relationship– Symbiosis

Ecosystems are Connected!

Ecosystems are studied as isolated systems BUT

All ecosystems are interconnected by– Proximity– Migratory patterns– Atmosphere (wind patterns)– Hydrology of Earth (groundwater flows, rivers)

THE END!