Chapter 18: Introduction to Ecology

Section 1 Vocabulary Pretest

1. Ecology

2. Interdependence

3. Ecological Model

4. Biosphere

5. Ecosystem

6. Community

7. Population

A. Thin zone of Earth that supports life

B. All organisms living in a certain area

C. All the members of one species in one area

D. Study of the relationship of organisms and their environment

E. All living things depend on other living things

F. All living and nonliving parts of an environment

G. Used to study the complexity of ecosystems

Answer Key

1. Ecology D

2. Interdependence E

3. Ecological Model G

4. Biosphere A

5. Ecosystem F

6. Community B

7. Population C

Ecology and Interdependence• Ecology is the study of the interactions

between organisms and the living and nonliving components of their environment.

– Interdependence is a key theme found throughout ecology.

– Living things depend on each other in complex ways for survival.

– Ecological models can be

used to study this complexity.

Levels of Organization• The hierarchy of environmental organization

from largest to smallest is: Biosphere, Ecosystems, Communities, Populations, and Organisms.

• Biosphere —thin zone of the Earth that supports life.

– 20 km thick from the bottom of the ocean to the lowest atmosphere.

– Three parts:

• lithosphere—land on the surface

• hydrosphere—water on the Earth

• atmosphere—air that surrounds Earth

Ecosystems• Biosphere is made of many smaller parts called

ecosystems.• Ecosystem—all living and nonliving parts of an

environment. Every ecosystem is able to support itself and has both biotic and abiotic factors:– Biotic factors—living organisms– Abiotic factors—nonliving parts: air, water, sunlight,

soil, temperature, pH, humidity, salinity, oxygen concentration, availability of nitrogen, etc. They are not constant—vary from place to place and over time.

• Examples: pond, garden, riverbank, puddle of water.

Communities and Populations

• Each ecosystem is made up of one or more communities.– Community—all the organisms

living in a certain area.

Example: pond community

• Each community is made up of populations.– Population—all the organisms of

the same species living in the same area.

Example: frogs in a pond

Section 2 Vocabulary Pretest1. Habitat

2. Biotic factor

3. Abiotic factor

4. Tolerance curve

5. Acclimation

6. Conformer

7. Regulator

8. Dormancy

9. Migration

10. Niche

11. Generalist

12. Specialist

A. Nonliving things

B. Living things

C. Place where an organism lives

D. Adjusting tolerance to abiotic factors

E. Cannot regulate internal conditions

F. Range of conditions that can be stood

G. Temporarily moving away

H. Temporarily not growing

I. Organisms job or role

J. Organism with narrow niche

K. Organism with broad niche

L. Can regulate internal conditions

Answer Key1. Habitat C

2. Biotic factor B

3. Abiotic factor A

4. Tolerance curve F

5. Acclimation D

6. Conformer E

7. Regulator L

8. Dormancy H

9. Migration G

10. Niche I

11. Generalist K

12. Specialist J

Surviving in an Ecosystem

• Each organism has a limited range of environmental conditions in which they can survive.– The range for a particular factor can be

measured using a tolerance curve– Some organisms can adjust their tolerance to

abiotic factors through the process of acclimation.

• Happens within an organism’s lifetime (not like adaptation)

Strategies for Tolerance

• Two strategies exist to deal with fluctuations in environments. – Conformers—organisms who do not regulate

their internal conditions; they change with the environment. Ex: ectothermic animals

– Regulators—organisms that use energy to control some of their internal conditions.

Ex: endothermic animals

Escaping Unfavorable Conditions

• Sometimes, adjusting isn’t possible and organisms must temporarily escape.Ex: Lizard hiding in the shade

Seed dormancy or animal hibernation

Migration

Habitats and Niches

• Habitat—place where an organism lives. It provides food, water, shelter, and a place to reproduce. Example: a woodpecker’s habitat is the trees in a forest.

• Niche—everything an organism does and everything it needs in its habitat. It is often defined as an organism’s job or role in its community. Example: a woodpecker’s niche is catching and eating insects.

Generalist vs. Specialist

• Generalist—species with broad niches– Ex: opossum (eats

almost anything)

• Specialist—species with narrow niches– Ex: koala (eats

eucalyptus leaves only)

Section 3 Vocabulary Pretest

1. Producer

2. Chemosynthesis

3. Gross primary productivity

4. Biomass

5. Net primary productivity

6. Consumer

7. Herbivore

A. An organism that eats food

B. An organism that makes food

C. An organism that eats plants only

D. An organism that uses chemicals to generate energy

E. Rate at which biomass accumulates

F. Rate at which producers capture energy from sunlight by producing organic compounds

G. All organic material produced in an ecosystem

8. Carnivore

9. Omnivore

10. Detritivore

11. Decomposer

12. Trophic level

13. Food chain

14. Food web

H. An organism that eats both producers and consumers

I. Model of the flow of energy through an ecosystem

J. An organism that breaks down organic material by causing decay

K. An organism that feeds on the “wastes” of an ecosystem

L. An organism that eats other consumers.

M. Many food chains combined

N. An organism’s position in a sequence of energy transfers

Answer Key1. Producer B

2. Chemosynthesis D

3. Gross primary productivity F

4. Biomass G

5. Net primary productivity E

6. Consumer A

7. Herbivore C

8. Carnivore L

9. Omnivore H

10. Detritivore K

11. Decomposer J

12. Trophic level N

13. Food chain I

14. Food web M

Energy and the Environment• Sunlight—main source of energy in an ecosystem.

– In photosynthesis, plants change light energy from the sun into chemical energy stored in food.

– Some of the plant’s food energy is used for their own growth and reproduction. The rest is stored.

– Animals eat the plants and use the stored food for energy for growth, reproduction and movement.

Ecological Classification of Organisms

• Ecologists classify organisms into two major groups according to the way they get food:– Producers—make food– Consumers—eat food

Producers

• Producers—make or produce their own food. Examples:

All plantsSome protists

Some bacteria

Types of Producers

• Photoautotrophs—use solar energy (photosynthesis) to produce sugar

• Chemoautotrophs—use energy stored in inorganic molecules (chemosynthesis) to produce carbohydrates

Measuring Productivity

• Gross primary productivity—the rate at which producers capture energy from sunlight by producing organic compounds.– Measured in biomass —organic material that has been produced

in an ecosystem

• Net primary productivity —rate at which biomass accumulates– Expressed in kcal/m2/yr or g/m2/yr.

– Calculated by: Gross primary productivity minus the rate of respiration in producers.

The graph shows the net primary productivity varies between biomes.The rainforest is 25 times greater than the desert of the same size.

Variations in light, temperature and precipitation account for the difference in terrestrial biomes. Variations in light and availability of nutrients accounts for differences in aquatic biomes.

Consumers• Consumers—get food by eating other

organisms or organic wastes. (Heterotrophs)

• Four types:

Herbivores—eat producers

Carnivores—eat other consumersOmnivores—eat producers and consumers

• Detritivores--feed on “wastes” (dead plants, animal wastes, and dead animal carcasses.) – A few are specifically classified as decomposers because they

cause decay and return important nutrients to the soil.

DetritivoresDecomposing Detritivores

Energy Flow• Energy flow through an

ecosystem can be illustrated using trophic levels (shows an organism’s position in a sequence of energy transfers)

• 1st level = producers

• 2nd level = herbivores

• 3rd and higher levels = predators

• Consumers are also grouped into feeding or trophic levels according to the foods they eat.

• Many organisms feed at more than one level, especially omnivores.

C1—first level consumers: eat plants

C2—second level consumers: eat C1 consumers

C3—third level consumers: eat C2 consumers

Food Chains• Food chain—model of the flow of energy

through the organisms of an ecosystem– Source of energy is the sun.– Arrows always point in the direction of the

flow of energy.– Energy that flows through a food chain is not

recycled. Sunlight must continue to flow through the biosphere to power the food chain.

C1 C2

C3

A food chain from a typical meadow ecosystem.

Food Webs• Food web —many food

chains combine to form a food web. It is generally a better model because it gives more information.– The members of a food

web can be identified by their trophic level.

– Many organisms function on more than one trophic level.

Which is a producer?Which are C1 consumers?Which are C2 consumers?Which is a C3 consumer?Which is a C4 consumer?

A complex food web from an aquatic ecosystem

Energy Pyramid• An energy pyramid is a model that

shows how the amount of energy decreases at each level of the food chain. – Some escape being eaten so their

energy is never transferred to the next level.

– Animals gain only a small amount of energy from the food they eat. Some parts of prey cannot be broken down for food (Ex: antlers and hoofs)

– Much of the energy is used up or is released as heat energy.

– Therefore, fewer organisms can be supported at each level of the pyramid.

A kilocalorie is ameasure of energy. The energy transferfrom one level to the next is about 10 %.For example:if there are 1,000 kcal atone level, only100 kcal are transferred tothe next. Thus each level cansupport fewerand fewer

organisms.

Cycles in Nature

• Many of the abiotic factors in an ecosystem pass through cycles that allow the substances to be used and reused.

• Four important cycles of abiotic substances include:– Water cycle– Carbon cycle– Nitrogen cycle– Phosphorus cycle

Water Cycle• Water also passes through both living and

nonliving parts of the environment. The water cycle is maintained by evaporation, transpiration, condensation and precipitation.

• Evaporation = adds water as vapor to the atmosphere. Water evaporates as water, soil, and living bodies heat up.

• Transpiration = evaporation of water from plants…causes them to take in more water.

• Condensation = change of water from a gas to a liquid…causes the formation of clouds in the water cycle.

• Precipitation = the return of water from the atmosphere…the amount of water the atmosphere can hold depends on temperature and air pressure…when clouds become saturated with water vapor, precipitation falls.

– Types: Rain, snow, sleet, hail and fog

Carbon Cycle• Photosynthesis and cellular respiration form the basis of

the carbon cycle.

• In the past 150 years, atmospheric carbon dioxide has risen more than 30%..mostly due to the burning of fossil fuels

Nitrogen Cycle• Air is 78% nitrogen gas. Most organisms cannot use nitrogen in this form.

• Nitrogen-fixing bacteria change nitrogen gas into nitrates which can be used by living things to make proteins and nucleic acids.

– Live in the soil and on the roots of certain plants (beans, peas, clover and alfalfa).

– Receive carbohydrates from plants and produce nitrogen for plants

– Release extra nitrogen into the soil.

• Decomposers--make the nitrogen from decaying organisms and wastes available in the soil by turning it to ammonia (NH3) which changes in the soil to ammonium (NH4

+) in a process called ammonification.

• Soil bacteria turns ammonium into nitrites (NO2-) and nitrates (NO3

-) in a process called nitrification. Plants can use the nitrates and then animals can eat the plants.

• Anaerobic bacteria return nitrogen to the air by breaking down soil nitrates in the process of denitrification.

Phosphorus Cycle• Phosphorus is necessary for healthy bones, teeth, and the formation of

DNA and RNA.

• The erosion of rocks is important in adding phosphorus to the soil and water.

• Excreted wastes and decaying organisms also add phosphorus to soil and water.

• Plants absorb phosphorus. Animals get phosphorus from plants.