EcologySection 18.1

Definition:• The study of the interactions between

organisms and their environment• Interdependence of organisms and their

environment

Levels of Organization

1. Biosphere

2. Ecosystem

3. Community

4. Population

5. Organism

Biosphere

• The Earth & the atmosphere that supports life

• “Thin film of life covering a lifeless planet”

Ecosystem

•All organisms & nonliving environment in a given place

–Organisms + water, pH, minerals, etc.

•Formed by the interactions of organisms and the enviro.

Community

• All of the interacting organisms in an ecosystem– Living things only!

Population

• All the members of ONE species living in one place at one time

Organism

• Open systems that exchange materials and energy with their enviro.

• ONE member of ONE species living in one place at one time

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Ecology of OrganismsSection 18.2

Habitat

• Where organisms live

• Contains abiotic and biotic factors– Abiotic: nonliving components

• Ex) sunlight, water, soil

– Biotic: living components• Ex) plants, animals, predators

Tolerance Range

• The range of abiotic conditions where the organism can still perform all activities for life

A

B

C

C

A & C = poor performanceB = peak performance

Acclimation

•When an organism adjusts its tolerance to an abiotic factor

•Ex) Moving from room to room with different temperatures

Control of Internal Conditions

• Conformers: organisms that DO NOT regulate their internal environment– “cold blooded”

• Regulators: organisms that DO regulate their internal environment– “warm blooded”

Escape from the Habitat

• Dormancy: a state of reduced activity for the organism– Hibernation

• Migration: movement of organism to a favorable habitat– Immigration: movement into a

habitat– Emigration: movement out of a

habitat

Niche

• The way of life for a species

• The role the species plays on its environment

Niche includes:

• Tolerable conditions for organism• Methods to obtain resources• Number of offspring per year• Time of reproduction• Any other interactions with the

environment

• ETC.

2 Types of Niches

• Fundamental Niche: the range of conditions a species could POTENTIALLY tolerate and the range of resources it could POTENTIALLY use.

• Realized Niche: the range of conditions and resources the species ACTUALLY tolerates and uses.

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Niche Differences

• A species’ niche can change within its lifespan

• Generalist: species with a broad niche

• Specialist: species with a narrow niche

Specialist

Generalist

Question:

•Which type can adapt to a changing environment better?

–Generalist or specialist?

•Why?

18-3 Energy Transfer

Energy Why do organisms need energy?

Maintain HOMEOSTASIS, growth, reproduction, etc.

How does energy affect an ecosystem?Determines how many and what kind

of organisms live in an ecosystem.

**The flow of materials in an ecosystem is cyclic, but the flow of energy is unidirectional!

Energy Flow:• The sun is the ultimate source of energy• The PRODUCERS use this energy to make

“food” energy for themselves and for the CONSUMERS

• video: how ecosystems work

How energy and inorganic nutrients flow through an ecosystem:

The nutrients are recycled…the energy is not!

Trophic LevelsThe organism’s position in the sequence of energy transfers.

A.K.A. Trophic Level is a group of organisms whose feeding source is the same number of steps from the Sun.

Autotrophs (producers) = 1st level, perform photosynthesis

–LARGEST

Heterotrophs (consumers) = 2nd level and above, Herbivores, Omnivores, Carnivores, Decomposers

• Omnivores (Humans)– Eat Plants & Animals

• Detritivores (Scavengers)– Feed On Dead Plant & Animal

Remains (buzzards)• Decomposers

– Fungi & Bacteria

• Herbivores– Eat Only Plants

• Carnivores– Eat Only Other Animals

Energy Gain by Trophic Levels:• The 10% Law: at each trophic level, the

energy stored in an organism is about 1/10 that of the level below it  (10%).

Implications on the ecosystem: Because energy diminishes at each

successive trophic level, few ecosystems can contain more than 4 or 5 trophic levels.

Organisms at higher levels (large carnivores) tend to be fewer in number than those at lower levels (producers).

Food Chain

• A single pathway of feeding (and energy transfer) relationships among organisms in an ecosystem.

Ex) Food chain

Food Web

• A diagram of the interrelated food chains in an ecosystem.

• More accurate description of the ecosystem.

Can you now answer these questions?

1.Contrast between producers and consumers.

2.Explain the important role of decomposers in an ecosystem.

3.Explain why an ecosystem usually contains only a few trophic levels.

4.What is the difference between an organism’s niche and its habitat?

5.List 2 sources that add carbon to the carbon cycle.

Energy flows through an ecosystem and nutrients cycle in an ecosystem.

Ecosystem Recycling (18.4)

The Water Cycle• Water is essential to all organisms • liquid water is the primary physical

phase in which water is used

Reservoirs:

– 97% of the biosphere’s water is

contained in the oceans

– 2% is in glaciers and polar ice caps

– 1% is in lakes, rivers, and groundwater

Water Cycle Steps:  Evaporation- from lakes, rivers, and oceans

 Transpiration-from plants and trees

 Condenstation – cloud formation

Precipitation – rain, snow, sleet, hail

 Runoff or Returned-back into the cycle

Groundwater- water in soil or in

underground formations of porous rock.

The Water Cycle

The Carbon Cycle: Use CO2: Photosynthesis

Release CO2: Combustion Death and decay Cellular

Respiration

Human Influences

Atmospheric CO2 has risen more than 30% in the past 150 years. Burning of fossil fuels- coal, oil,

and natural gas Burning down the tropical rain

forest video

The Nitrogen Cycle

Nitrogen Fixation: the process of converting atmospheric nitrogen (N2) into nitrate, its useable form.

Nitrogen-fixing bacteria: turn nitrogen gas into a useable form. Located in soil and the roots of some plants.

Ammonification: bacteria decompose dead matter and release the nitrogen they contain as ammonia

Key Terms

So… How do plants and animals get nitrogen?

Phosphorous Cycle obtained by plants from water and soil, and

animals from the food they eat used to form bones, teeth, and molecules such

as DNA and RNA Source: erosion of rocks into the soil or water,

decomposition of organisms, and fertilizers

Biomagnification: The increase in

concentration of a substance in a food chain

The substance cannot be broken down or excreted by the animal; builds up in tissues Pesticide Heavy metal

simulation

Example

An anchovy eats zooplankton that have tiny amounts of mercury that the zooplankton has picked up from the water throughout the anchovie’s lifespan. A tuna eats many of these anchovies over its life, accumulating the mercury in each of those anchovies into its body. If the mercury stunts the growth of the anchovies, that tuna is required to eat more little fish to stay alive. Because there are more little fish being eaten, the mercury content is magnified.

Food Web Matching Game

Cut the individual organisms boxes

off the bottom of the game board Your job is to match the organisms to their position on

the food web The trophic level tables provide you with all of the

info. that you need When you decide on the placement of an organism,

look up the clue the corresponds to your placement. If your placement is correct, the clue will read “Correct!”