ECOLOGY

Chapters 24, 25 and 28

• Ecology = scientific study of interactions between organisms, and between organisms and their environment

• Eco comes from the Greek word “oikos” which means “house,” so ecology is the study of YOUR house-Earth!

• Nature has many “houses”– Biosphere = all parts of our earth where life exists

• No life is an island unto itself

• Life depends on interactions between living and non-living parts of the biosphere

• All life is inter-dependent– Birds eat worms that live on leaves of trees, trees depend on soil,

sunlight and water– Humans eat plants and animals, breathe air, and drink water,

animals eat plants or other animals, plants depend on soil, water and sunlight

Bio = lifeSphere = circle

Biosphere = The circle of Life!

Parts of an Ecosystem• Biotic factors = living, biological,

factors that shape ecosystems• Trees, mushrooms, bacteria, animals, flowers, etc.

• Abiotic factors = physical or non-living factors that shape ecosystems

• Rocks, water, soil, air, sunlight

• Biotic + Abiotic factors determine the survival and growth of an organism and the productivity of the ecosystem

Biotic factors

Abiotic factors

Group of organisms so similar to one another they can breed and produce fertile offspring

Group of ecosystems with the same climate and similar dominant communities (desert, tundra, taiga, temperate forest, tropical rainforest, artic)

6 Levels of Organization

Collection of all organisms that live in a particular place, together with the non-living parts of their environment

Assemblies of different populations living in a defined area

2. Ecosystem

3. Communities

5. Species

4. Populations

1. Biome

Groups of individuals belonging to the same species and living in the same area

One member of a species6. Individual

Populations

• Three key characteristics of population structure:

1. range 2. dispersion - random - uniformly spaced - clumped spacing 3. size of population

Populations

• Metapopulation

• Source-sink Metapopulation

• Demography

• Generation Time

• r-strategists vs. k-strategists

Exponential and Logistic Growth

• Exponential Growth = occurs when individuals in a population reproduce at a constant rate

• Under ideal conditions with unlimited resources, a population will grow exponentially

• Logistic growth occurs when a population’s growth slows or stops

• Carrying Capacity = # of individuals the environment can support without undergoing deterioration

Nu

mb

er o

f M

agg

ots

Carrying capacity

Time (hours)

Maggots in a Garbage Can

Exponential Growth Logistic Growth

Population Growth

• Biotic Potential: a population growing without limits

• Rate of population increase:

b=birthrate d= deathrate e=emmigration

i= immigration

r = (b - d) + (i – e)

Limits to Growth• Limiting factors = factor that causes

population growth to decrease• Competition, predation, parasitism, drought and

other climate conditions, human disturbance

• Density-dependent factors = limiting factors that depend on the populations size

• Competition, predation, parasitism, disease

• Competition = when organisms compete with each other for resources– Too many people, too few jobs– Too many deer, not enough food

Density-Independent Factors

• Density-Independent Factors affect all populations no matter what the size

• Weather, natural disasters, seasonal cycles, certain human activities (damming rivers, clear cutting forests)

– The Tsunami in Sri Lanka affected all populations there, human, animal and plant

– Volcanic eruption of Mt. St. Helens affected all populations in that area

– Mud slides in California have affected humans and all other non-human populations

How We Grew So Fast

Agriculturebegins

Plowingand

irrigation

Bubonicplague

IndustrialRevolution

begins

We had a long, slow start, but improvements in medicine, sanitation, agriculture, energy use, and technology has allowed our population to grow exponentially. So, what’s going to happen to us if this type of population growth continues?

We will reach our carrying capacity – resources will be exhausted, disease, famine, wars, natural disasters, or we’ll find a way to emigrate to new planets and start all over again.

Human Population Growth• In 2000, the world had 6.1 billion human inhabitants. • This number could rise to more than 9 billion in the next

50 years.

Low growth rate

Low growth rate

Low growth rateHigher growth rate

Explosive growth rate

Very high growth rate

Underdeveloped countries tend to have higher population growth rates, but they also have higher death rates – disease, famine, etc.

Age Structures

U.S. Population Rwandan Population

Age-structure diagrams = (population profiles) graph the numbers of people in different age groups in the population

Who can reproduce

Who will reproduce

More older people (no reproducing)

What’s Going To Happen?• At the 2000 growth rate of 1.4 percent, the

world's 6.1 billion population yields an annual increase of about 85 million people.

• Because of the large and increasing population size, the number of people added to the global population will remain high for several decades, even as growth rates continue to decline.

• Between 2000 and 2030, nearly 100 percent of this annual growth will occur in the less developed countries in Africa, Asia, and Latin America

• Growth rates of >1.9 percent mean that populations would double in about 36 years, if these rates continue

• So, when YOU are ~54 yrs old, there will be ~12.2 billion people on Earth- good luck finding a job!

Copyright 2005, Population Reference Bureau

Who Lives in a Community• Habitat = an organism’s address,

where it lives• Niche = an organism’s occupation,

what it does in its habitat– Includes:

• Where it fits into the food web• Type of food it eats• How it obtains food• When and how it reproduces

• No 2 species can share the SAME habitat and the SAME niche when resources are limiting

• But, different species can occupy similar niches in the same habitat

Bernie’s niche

No one else could do MY job.

Community Ecology

• Niche:

Sum total of all the ways an organism utilizes the resources of its environment

(space utilization, food consumption, mating behavior, temperature range, etc.)

**Habitat is a place, niche is a pattern of living

**Fundamental Niche vs. Realized Niche

Community Interactions

1. Competition

2. Predation

3. Three forms of symbiosis: any relationship in which two species live closely together

Community Ecology

• Interspecific competition• Intraspecific competition• Interference Competition• Exploitative competition• Competitive Exclusion• Resource Partitioning - sympatric species - character displacement

Predation

• Populations in nature are controlled by predation

• Predator-Prey relationships = one of the best mechanisms for population control

60

50

40

30

20

0

1955 1960 1965 1970 1975 1980 1985 1990 1995

2000

1600

1200

800

4000

2400

Moose Wolves

Relationship Between Wolves and Moose on Royale Island (Lake Superior)

Defense Against Predators

• Plants - Morphological defenses - Chemical defenses• Animals Defensive Coloration - warning/aposematic - cryptic• Chemical Defenses• Mimicry

Symbiosis

• Commensalism

• Mutualism

• Parasitism

Energy Flow• Everything needs energy

• What is the ultimate source of energy?• The Sun!

• Energy flows through an ecosystem

• Producers = obtain energy directly from the sun or capture energy from chemicals– Autotrophs = plants, some algae, and certain

bacteria can capture the sun’s energy or use chemicals to produce their own food

– Essential to the flow of energy through an ecosystem– Autotrophs are producers

Section 3-2Producers produce food

Auto = self

Troph = nourishment

Consumers• Heterotrophs = organisms that rely on

other organisms for their energy and food supply

• You consume animals and plants to obtain energy, you are a CONSUMER

• Types of heterotrophs:– Herbivore – eats only plants– Carnivore- eats only animals– Omnivore- eats plants and animals– Detritivore – eats plant and animal remains, dead things– Decomposers – breaks down organic matter

Food Chains• Energy flows in only ONE direction, from

the sun to autotrophs then heterotrophs• Who eats who forms a network of feeding

relationships called a Food Chain• Food Chain = series of steps in which organisms

transfer energy by eating or being eaten• ALL food chains begin with producers

Producers 1st level consumers 2nd level consumers

= Food Chain

Food Webs• Life isn’t simple, most ecosystems consist

of a series of food chains called Food Webs• Food Web = links together all the Food

Chains in an ecosystem

= Food Web

heron

marsh hawk

shrew

clapper rail (omnivore)

plankton eating fish

harvest mouse

(omnivore)

ribbed mussel

marsh grassalgae

pickle weed

detritus

zooplankton

sandhopper

decomposers producers

herbivores

1st level consumers

Top level carnivores

Food Web

Each step in a food chain or web is called a Trophic Level.

Each trophic level depends on the level above and below it.

Ecological Pyramids

• Amounts of energy and matter in an ecosystem can be represented by an ecological pyramid

• 10% Rule: only about 10% of the energy available within one trophic level is transferred to organisms at the next level Energy Pyramid

1st order consumers = 10%

2nd order consumers = 1%

3rd order consumers = 0.1%

Producers = 100%100%

10%

1%0.1%

Where did the 99.9% of the energy go?

Pyramid of Numbers• Each trophic level harvests only about one

tenth of energy from the level below it

Shows the relative number of individual organisms at each trophic level.

Less top predators like the eagle

More 1st and 2nd order consumers, the prey

Producers, like plants, are the most abundant

Biomass Pyramid• Biomass = total amount of living

tissue within a given trophic level– Usually expressed in grams of organic matter/unit area– Biomass pyramid represents total amount of potential food (at

each trophic level)

Typically, the greatest biomass is at the base of the pyramid.

500 grams of chicken

1500 grams of grain

Cycles of Matter• Unlike the 1-way flow of energy in an

ecosystem, matter recycles in and between ecosystems

• Biogeochemical Cycles = elements, chemical compounds, and other forms of matter are passed from 1 organism to another and to other parts of the biosphere– Water cycle– Nutrient cycles

• Nitrogen cycle• Phosphorous cycle• Carbon cycle

Water Cycle• All living things depend on H2O

to survive

• It moves between the ocean, atmosphere and land, constantly recycling

• Evaporation = process where H2O changes from liquid to atmospheric gas– Evaporation is from oceans or other

bodies of H2O

• Transpiration = H2O entering atmosphere by evaporating from leaves of plants

condensationprecipitation

run off

seepage

root uptake

transpirationevaporation

Water Cycle

Nutrient Cycles• Nutrients = all the chemical substances

an organism needs to sustain life– Producers obtain nutrients from their environment– Consumers obtain nutrients by eating other organisms

• Every living organism needs nutrients to build tissues and carry out essential life functions

• Like H2O, nutrients are passed between organisms and the environment through biogeochemical processes

• The 3 Nutrient Cycles are:– Carbon cycle - Nitrogen cycle– Phosphorous cycle

Carbon Cycle• You are full of CHON, but Carbon

is the main ingredient of living tissue• 4 main types of processes move carbon

through its cycle:1. Biological processes = photosynthesis, respiration,

decomposition2. Geochemical processes = erosion and volcanic activity

release CO2 into the air and oceans3. Mixed biogeochemical processes = burial and

decomposition of dead organisms, and their turning into fossil fuels (coal, oil, natural gas)

4. Human activities = mining, cutting and burning forests, burning fossil fuels,= release CO2 into air

Carbon Cycle

CO2 in atmosphere

CO2 in ocean

Carbon is found in several large reservoirs in the biosphere:In the atmosphere –CO2 gasIn the oceans- dissolved CO2

On land –in organisms, rocks and soilUnderground –coal, oil and calcium carbonate rock

Nitrogen Cycle• All organisms require nitrogen to make

amino acids, the building blocks of proteins• Different forms of naturally occurring Nitrogen:

• Nitrogen gas (N2)- makes up 78% of Earth’s atmosphere

• Nitrogen containing substances – such as ammonia (NH3) and nitrate ions (NO2

-)

• Some bacteria “fix” nitrogen from the air, converting nitrogen gas into ammonia = Nitrogen fixation (Bacteria live on roots of plants and in soil)

• Consumers eat the plants and use the nitrogen to make proteins

• Denitrification = when soil bacteria convert nitrates into nitrogen gas, which is released into the air

Phosphorous Cycle• Phosphorous (P) is essential to living

organisms because it forms part of important life-sustaining molecules like DNA and RNA

• Despite its importance, P is not very common in the biosphere– P exists in the form of inorganic phosphate found in

rocks and soil– P washes into rivers, streams and lakes where it

dissolves and eventually ends up in the ocean– P also remains on land where it cycles between

organisms and the soil

Succession

• Primary Succession:

Occurs on bare, lifeless substrates such as lava flows

1. Lichens are PIONEER SPECIES that create soil pockets through acidic secretions

2. Mosses (build soil nutrients) and eventually alders follow

Fig. 25.23

Secondary Succession

• Occurs in an area where an existing community has been destroyed

Ex. Forest fire

Keystone Species:Species that have particularly strong effects on the

composition of communitiesEx. Beavers: construct dams and change a flowing

stream into a pond, creating a new habitat for many plant and animal species.

Fig. 25.21