Introduction to EcologyChapter 18

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

• “Thin film of life covering a lifeless planet”

Ecosystem•All organisms & nonliving environment in a given place

–Organisms + water, pH, minerals, etc.

Community

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

Population

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

Organism

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

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

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.

Questions:

• Which niche is larger?

• Why?

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

EnergyWhy 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.

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

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.

Common Trophic Levels:•First = Producers (Autotrophs)

–LARGEST

•Second = Herbivores (Heterotrophs, Consumers)

•Third and above = All other consumers (Heterotrophs, Omnivores, Carnivores, Decomposers)

–SMALLEST

• Omnivores (Humans)– Eat Plants & Animals

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

Remains (buzzards)• Decomposers

– Fungi & Bacteria

ConsumersHeterotrophs eat other organisms

to obtain energy. (e.g. animals)• Herbivores

– Eat Only Plants• Carnivores

– Eat Only Other Animals

Energy Gain by Trophic Levels:• 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)

Water Cycle Steps:  EVAPORATION from lakes, rivers, and oceans. 

 TRANSPIRATION from plants and trees.

 CONDENSATION – Cloud Formation

PRECIPITATION – Rain, Snow, Sleet, Hail.

 RUN OFF, or

RETURNED back into the Cycle.

Groundwater- water in soil or in underground formations of porous rock.

The Water Cycle

The Carbon Cycle

Cellular Respiration

Photosynthesis

Combustion

Death and decomposition

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

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