Ecology

Ecology

Chapters 2-5

Define ecology

• Study of interactions among organisms and between organisms and their environment

• Biosphere – all the parts of the planet in which life exists including land, ocean, and atmosphere– Interactions within biosphere create a web of

interdependence between the organisms and their environment

The Biosphere

Principles of Ecology

Biotic FactorsPrinciples of Ecology

Living factors in an organism’s environmentEx: predation

Abiotic Factors

Nonliving factors in an organism’s environment

Ex: sunlight, temperature

Levels of Organization


Levels increase in complexity as the numbers and interactions between organisms increase.

organismpopulationbiological communityecosystembiome

biosphere

The lowest level of organization is the individual organism itself.


Organisms of a single species that share the same geographic location at the same time make up a population.

A biological community is a group of interacting populations that occupy the same geographic area at the same time.

Organisms and Their Relationships

An ecosystem is a biological community and all of the abiotic factors that affect it.


A biome is a large group of ecosystems that share the same climate and have similar types of communities.

Ecosystem Interactions


A habitat is an area where an organism lives.

A niche is the role or position that an organism has in its environment.

Community Interactions


Competition

Occurs when more than one organism uses a resource at the same time

Predation

Many species get their food by eating other organisms.

Symbiotic RelationshipsPrinciples of Ecology

Both species benefit

Mutualism

Commensalism

Parasitism

The close relationship that exists when two or more species live together

One organism benefits, the other is not helped or harmed

One organism is helped, the other is harmed

Energy in an Ecosystem

Autotrophs


Organism that collects energy from sunlight or inorganic substances to produce food

Heterotrophs Organism that

gets it energy requirements by

consuming other organisms

A lynx is a heterotroph.

AKA: consumersTypes:

Herbivores: plant eatersCarnivores: meat eatersOmnivores: plant and meat eatersDetritivores: eat plant and animal remains

ecosystem, and return nutrients to the soil, air, and waterwhere thenutrients can be reused by organisms.

Detritivores eat fragments of dead matter in an


Fungus


Models of Energy Flow

Food chains and food webs model the energy flow through an ecosystem.

Each step in a food chain or food web is called a trophic level.

How does energy flow through an ecosystem?

• In one direction- from sun to producers then to consumers


Food Chains

A food chain is a simple model that shows how energy flows through an ecosystem.


Food Webs

A food web is a model representing the many interconnected food chains and pathways in which energy flows through a group of organisms.


Ecological Pyramids

A diagram that can show the relative amounts of energy, biomass, or numbers of organisms at each trophic level in an organism

What are trophic levels?• Trophic levels represent each step in a food

chain– 1st level = producers– 2nd level = herbivores– 3rd level and up = carnivores and omnivores

How can we show all of the energy in an ecosystem?

• Ecological pyramids – shows amounts of energy or matter within each trophic level

• Energy pyramids – shows amounts of energy transferred to the next trophic level is only about 10% of the previous level

• Biomass pyramid – shows total amount of living tissue

• Numbers pyramid – shows #s of individuals in each trophic level

Cycles in the Biosphere

Cycling of Matter


Energy is transformed into usable forms to support the functions of an ecosystem.

The cycling of nutrients in the biosphere involves both matter in living organisms and physical processes found in the environment such as weathering.

How does water move around an ecosystem?• The water cycle – water

continually moves from the ocean to the atmosphere to the land and back to atmosphere– Evaporation – change from

liquid to gas – from oceans or any standing water or lakes, etc.

– Transpiration – evaporation from plant leaves

– Condensation – gas to liquid in atmosphere forming clouds

– Precipitation – liquid falls back to the earth where it drains into oceans, rivers, and lakes or soaks into the ground for storage

– Run-Off- liquid runs back into water source

– Percolation- liquid seeps into the soil.

The Water CyclePrinciples of Ecology



Freshwater constitutes only about 3 percent of all water on Earth.

About 69 percent of all freshwater is found in ice caps and glaciers.

Approximately 90 percent of water vapor evaporates from oceans, lakes, and rivers; 10 percent evaporates from the surface of plants


The Carbon and Oxygen Cycles



Carbon and oxygen recycle relatively quickly through living organisms.

Carbon and oxygen often make up molecules essential for life.


The Nitrogen Cycle

The capture and conversion of nitrogen into a form that is useable by plants is called nitrogen fixation.



Consumers get nitrogen by eating plants or animals that contain nitrogen.

Nitrogen enters the food web when plants absorb nitrogen compounds from soil.


Nitrogen is returned to the soil in several ways:

Animals urinate.

Organisms die.

Organisms convert ammonia into nitrogen compounds.

Denitrification


The Phosphorus Cycle


Limiting Factors

Any abiotic factor or biotic factor that restricts the numbers, reproduction, or distribution of organisms is called a limiting factor.

Communities, Biomes, and Ecosystems

Includes sunlight, climate, temperature, water, nutrients, fire, soil chemistry, and space, and other living things

Range of Tolerance

An upper limit and lower limit that define the conditions in which an organism can survive


The ability of any organism to survive when subjected to abiotic factors or biotic factors is called tolerance.

How do ecosystems change over time?

• Always changing in response to natural and human disturbances– Older inhabitants die out, new organisms move in

• Ecological succession – predictable changes in a community over time; the change in an ecosystem that happens when one community replaces another as a result of changing abiotic and biotic factors – Caused by slow changes in physical environment– Caused by sudden natural disturbance

Ecological Succession


There are two types of ecological succession—primary succession and secondary succession.

What is primary succession?• Succession on land

where no soil previously existed– Hardened volcanic lava

or ash– Rocks exposed from

glacier melt

• Pioneer species – 1st to populate an area– i.e. Lichens– Creates soil


What is secondary succession?

• Follows a community changing disturbance– Wild fires, humans clearing land

• Climax Communities – ending point of succession – mature stable community– Still goes through change over time


Secondary Succession after a fire

Secondary Succession of

a

Lake


What role does climate play?

• Weather – day to day atmospheric conditions at a certain place

• Climate – average year-round conditions of temperature and precipitation

• Causes of climate– Trapping of heat by atmosphere– Latitude– Transport of heat by winds and

currents

What is the greenhouse effect?

• Gases in the atmosphere trap heat energy and maintain Earth’s temperature range

• Carbon dioxide, methane, water vapor

• Traps heat being released from the earth

• Naturally occurring• Magnified by the

burning of fossil fuels

What effect does latitude have on climate?

• Earth is tilted on it’s axis and receives varying angles of solar radiation at different latitudes.

• Creates 3 climate zones:– Tropical: at the equator,

hot– Temperate: middle

latitudes, hot and cold depending on season

– Polar: high latitudes, cold

Biomes are classified by their plants, temperature, and precipitation.


Tropical forests

Deserts

Temperate deciduous forestWhere we Live!

Tundra

• Permafrost

Chaparral: Shrubland

Coniferous forests

Savanna

Describe some aquatic ecosystems.• Determined by depth,

flow, temperature, and chemistry of overlying water

• Inhabitants specially adapted to each ecosystem

• Freshwater ecosystems– Flowing water – rivers,

streams, creeks– Standing water – lakes,

ponds

More aquatic ecosystems• Estuaries –

wetlands where rivers meet the sea, fresh and salt water – made of mostly detritivores– Salt marshes– Mangrove

swamps

Marine Ecosystems• Light zones

– Photic – well lit upper layer where organisms are able to carry out photosynthesis

– Aphotic – permanently dark zone bottom of ocean.

Population Density

The number of organisms per unit area

Spatial Distribution

Population Ecology

Dispersion is the pattern of spacing of a population.

Population Ecology

Exponential Growth Model Exponential growth occurs

when the growth rate is proportional to the size of the population.

if it has the perfect environment. Limited to short periods and small areas.

Population multiplies quickly.

All populations grow exponentially until

some limiting factor slows the population’s growth.

J-CurveThis is mostly unrealistic.

Population Ecology

Logistic Growth Model

The population’s growth slows or stops following exponential growth, at the population’s carrying capacity.

S-Curve

Population Ecology

Population Ecology

Population-Limiting Factors

There are two categories of limiting factors—density-independent factors and density-dependent factors.

Density-Independent Factors

Any factor in the environment that does not depend on the number of members in a population per unit area is a density-independent factor.

Population Ecology

Weather eventsFireHuman alterations of the landscapeAir, land, and water pollution

•Shows a “boom & bust” curve

Density-Dependent Factors

Any factor in the environment that depends on the number of members in a population per unit area is a density-dependent factor.

Population Ecology

Biotic factorsDiseaseCompetitionParasites

•Produces s-shaped curve

Population Ecology

The maximum number of individuals in a species that an environment can support for the long term is the carrying capacity.

Carrying capacity is limited by the energy, water, oxygen, and nutrients available.

Population Ecology

Reproductive Patterns

Species of organisms vary in the number of births per reproduction cycle, in the age that reproduction begins, and in the life span of the organism.

Population Ecology

An r-strategist is generally a small organism.

Short life span

Produces many offspringEx: Mice

The rate strategy, or r-strategy, is an adaptation for living in an environment where fluctuation in biotic or abiotic factors occur.

Population Ecology

A k-strategist is generally a larger organism.

Long life span

Produces few offspringEx: Elephant, Humans

The carrying-capacity strategy, or k-strategy, is an adaptation for living in stable environments.

Population Ecology

Population Growth Rate

The population growth rate (PGR) explains how fast a given population grows.

The natality of a population is the birthrate in a given time period.

Population Ecology

A population stops increasing when the number of births is less than the number of deaths or when emigration exceeds immigration.

Human Population Growth

The study of human population size, density, distribution, movement, and birth and death rates is demography.

Population Ecology

HUMAN POPULATION GROWTH

• Currently our growth is exponential.

• Exponential growth due to:– Advances in

technology– Energy development– Advances in agriculture– Transportation– Medicine

• We do not know our carrying capacity.

Human Population Growth Rate

Although the human population is still growing, the rate of its growth has slowed.

Population Ecology

Trends in Human Population Growth

Population trends can be altered by events such as disease and war.

Population Ecology

Human populationgrowth is not the same in all countries.

Zero population growth (ZPG) occurs when the birthrate equals the death rate.

Population Ecology

Zero Population Growth

Age Structure

Population Ecology

A population’s age structure is the number of males and females in each of three age groups:

pre-reproductive stage, reproductive stage, and post-reproductive stage.

Human Carrying Capacity

Population Ecology

Scientists are concerned about the human population reaching or exceeding the carrying capacity.

An important factor is the amount of resources from the biosphere that are used by each person.

Biodiversity and Conservation

Pollution

Pollution and atmospheric changes threaten biodiversity and global stability.

Biological magnification is the increasing concentration of toxic substances in organisms as trophic levels increase in a food chain or food web.

Threats to Biodiversity


Eutrophication

occurs when substances rich in nitrogen and phosphorus flow into waterways, causing extensive algae growth.

The algae use up the oxygen supply during their rapid growth and after their deaths during the decaying process.

Other organisms in the water suffocate.

Threats to Biodiversity

Resources that are replaced by natural processes faster than they are consumed are called renewable resources.


Resources that are found on Earth in limited amounts or those that are replaced by natural processes over extremely long periods of time are called nonrenewable resources.

Conserving Biodiversity

Documents

Ecology