EcologyChapters 34, 35, and 36

Ch 34: The BiosphereEcology is the study of the interactions of

organisms with their environment.

Levels of Organization

Ecologists study environmental interactions at several levels

From MOST complex to LEAST complex:

BiosphereEcosystemCommunityPopulationOrganism

1. BiosphereThe biosphere is the global ecosystem, the sum

of all the planet’s ecosystems. It is the MOST COMPLEX level of organization in ecology.

2. EcosystemThe next level of

organization is the ecosystem level (living and non-living components in an area).

Biotic vs. AbioticAn ecosystem includes all of the living and

non-living components in a certain area.Biotic components are living things like plants

and animals.Abiotic components are the non-living

components, such as temperature, energy, gases, water, nutrients, chemicals, rocks, and soil.

3. CommunityNext is the

community level, which is all of the organisms of different species that live in an area.

HabitatsA habitat is an environmental area in which

organisms live.Habitats include communities of organismsAbiotic factors also make up habitats (rivers, lakes,

temperature, oxygen)

4. PopulationThe next level is

population, an interbreeding group of individuals belonging to the same species and living in a particular geographic area.

5. OrganismThe lowest level of organization is the organism:

an individual living thing, such as a plant, animal, bacteria, fungus, etc.

BiomesA biome is a specific ecosystem, largely

determined by climate, vegetation, and the organisms that live there.

Aquatic BiomesSaltwater oceans cover 75% of the planet’s

surface.

Freshwater biomes include: lakes, ponds, rivers, streams, and wetlands.

Terrestrial Biomes (8)Terrestrial biomes are characterized by weather,

plants, and animals living in a certain area.

1. Tropical ForestsOccur in equatorial areas where the

temperature is warm and days are 11-12 hours long year-round.

They are one of the most complex biomes with a huge diversity of species.

2. SavannasDominated by grasses and scattered trees.

3. DesertsThe driest of all biomes, with low and

unpredictable rainfall, high temperatures, and dry air.

4. Chaparral = San DiegoRegions with dense,

spiny shrubs with tough, evergreen leaves.

Mild rainy winters and hot dry summers.

5. Temperate GrasslandsGrassy areas with few trees and long, cold

winters (Chicago)

6. Temperate Deciduous Forests

Forests with deciduous trees, cold winters and hot summers.

7. Coniferous ForestsCharacterized by

cone-bearing evergreen trees.

Also called the taiga.

The largest biome on earth.

8. The TundraBetween the taiga and permanently frozen polar

regions.

Treeless, but has permafrost: permanently frozen subsoil.

Biomes Videohttp://www.encyclopedia.com/video/WZGCZY47Y

S0-biomes-of-world.aspx

Biodiversity

Chapter 35: PopulationsPopulation Ecology studies the changes in

population size and the factors that regulate populations over time.

A population is a group of individuals of the same species that occupy the same general area.

Dispersion PatternsThe dispersion pattern of a population refers to

the way individuals are spaced within their area.Clumped: individuals live in small groups or

patches throughout the area. This is the most common pattern in nature.

Uniform: even pattern dispersion resulting from interactions and competitions between organisms.

Random: pattern less, unpredictable dispersion of organisms.

Dispersion Patterns

Random Clumped Uniform

Models of Population Growth

Exponential Growth gives an idealized picture of unregulated growth of a population.

It is an unrealistic, J-shaped curve

Exponential GrowthGrowth of a population is limited by population-

limiting factors, including: Foodwaterbreeding areahuntingCompetitionbirthdeath

Logistic Growth ModelsLogistic Growth Models

show population growth when you take into account limiting factors.

They are S-shaped and more realistic.

They level off at carrying capacity: maximum population size

Survivorship CurvesThere are 3 types of survivorship curves, I, II,

and III.

r and k selectionr-selection: species in which a high reproductive

rate is the chief determinant of their lives: weeds and insects.

k-selection: species that live lives in order to produce relatively few offspring that have a good chance of survival: mammals, people, birds.

Birth and Death RatesPopulation stability is reached when there is

zero population growth, when birth rates = death rates.

The age structure of a population affects how slowly or quickly the population grows. It shows how many people of each age are living in a country.

Figure 35.9B

RAPID GROWTH

Kenya

Male Female

Percent of population Percent of population Percent of population

SLOW GROWTH

United States

Male Female

ZERO GROWTH/DECREASE

Italy

Male Female

Ages 45+

Ages 15–44

Under15

Under15

Ages 45+

Ages 15–44

Chapter 36: CommunitiesA community is an assemblage of all the

populations of organisms living close enough together for potential interaction.

The biodiversity of a community is the variety of organisms that make it up. It includes:The total number of different species in the

communityThe relative abundance of the different species

NicheA niche is the position or function of an organism in a

community.

PredationIn predation, one

species eats another.

The predator is the consumer, the one who eats.

The prey is the food, the one being eaten.

SuccessionAfter a disturbance like a fire, storm, or flood,

the ecosystem transitions from nothing to new life, in a process called succession.

Primary succession happens when there is no soil present, such as after a volcano.

Secondary succession occurs where a disturbance has left some soil, such as after a fire.

Food chains and websFood chains and food webs show the flow of

ENERGY through an ecosystem.

All energy ultimately comes from the SUN.

Energy flowEnergy starts at the producer level (plants)

Then moves up to primary consumers (herbivores)

Then to secondary consumers (carnivores)

Followed by tertiary and quaternary consumers…

Figure 36.9A

TROPHIC LEVEL

Quaternaryconsumers

Tertiaryconsumers

Carnivore Carnivore

Carnivore Carnivore

Carnivore Carnivore

Herbivore Zooplankton

Plant Phytoplankton

Secondaryconsumers

Primaryconsumers

Producers

A TERRESTRIAL FOOD CHAIN AN AQUATIC FOOD CHAIN

ProducersProducers make food. They are also autotrophs,

and typically include plants.

ConsumersConsumers eat things. They are heterotrophs.

They include:Herbivores: eat plantsCarnivores: eat animals (meat)Omnivores: eat both plants and meat

DecomposersAll food chains and webs have decomposers or

detritivores

These organisms, including bacteria, worms, rodents, insects, catfish, fungus, and vultures, eat detritus, the dead material produced at every level of a food chain.

Food WebsA food web is a

network of food chains, and is a more realistic view of energy flow.

Every food web MUST include the SUN and DECOMPOSERS

Figure 36.10

Tertiaryandsecondaryconsumers

Secondaryandprimaryconsumers

Primaryconsumers

Producers

(Plants, algae,phytoplankton)

Detritivores

(Prokaryotes, fungi,certain animals)

Wastes anddead organisms

EnergyAs you go up a level in a food chain or web, only

10% of the energy from the level below is transferred to the next level. 90% is lost as HEAT.

Because the production pyramid tapers so sharply, a field of corn or other plant crops can support many more vegetarians than meat-eaters

Figure 36.12

Secondaryconsumers

Primaryconsumers

Producers

Humanvegetarians

Corn

Humanmeat-eaters

Cattle

Corn

TROPHIC LEVEL

ReviewName a producer.

What energy level would people be at?

What energy level would a mouse be at?

Name a secondary consumer.

Why can’t food chains grow more than 5 levels high? (think about energy transfer)

Food Web Videohttp://nasa.ibiblio.org/video/NASASciFiles/NASA

WF-TheInhabitableHabitat/qt/NASAWF-FoodWeb.mov

Nutrient CyclingIn food webs, energy only moves one way, up

trophic levels.

Nutrients & materials must be recycled between organisms and abiotic reservoirs

There are 4 main abiotic reservoirs:WaterCarbonNitrogenPhosphorus

The Water CycleThe water cycle is driven by heat from the sun.

Water cycles through Precipitation (rain)Evaporation (liquid to gas)Transpiration (liquid from plant leaves turns to

gas)

Figure 36.14

Solarheat

Precipitationover the sea(283)

Net movementof water vaporby wind (36)

Flow of waterfrom land to sea(36)

Water vaporover the sea

Oceans

Evaporationfrom the sea(319)

Evaporationandtranspiration(59)

Water vaporover the land

Precipitationover the land(95)

Surface waterand groundwater

The Carbon CycleCarbon is used by photosynthesis (CO2) and

produced by cellular respiration (CO2)

Carbon is needed to make anything organic: plants, animals, people…

Carbon from the atmosphere is turned into organic compounds (like glucose) by plants that do photosynthesis!

Burning wood and fossil fuels increases CO2 in the atmosphere.

Figure 36.15

CO2 in atmosphere

Cellular respiration

Higher-levelconsumers

Primaryconsumers

Plants,algae,

cyanobacteria

Photosynthesis

Wood andfossil fuels

Detritivores(soil microbes

and others) Detritus

Decomposition

Burning

The Nitrogen CycleNitrogen exists in the atmosphere as N2, but

that cannot be used by plants and animals.

It must be converted to ammonia (NH4 ) and nitrates (NO3 )

Bacteria play major roles in this cycle

Most useable nitrogen is stored in the soil

Figure 36.16

Nitrogen (N2) in atmosphere

Amino acidsand proteins in

plants and animalsAssimilationby plants

Denitrifyingbacteria

Nitrates(NO3

–)

Nitrifyingbacteria

Detritus

Detritivores

Decomposition

Ammonium (NH4+)

Nitrogenfixation

Nitrogen-fixingbacteria in soil

Nitrogen-fixingbacteria in root

nodules of legumes

Nitrogenfixation

The Phosphorus CycleThe phosphorus cycle depends on weathering of

rock, and adding minerals to the soil.

Plants need phosphorus to grow

Consumers get phosphorus by eating plants.

Figure 36.17

Upliftingof rock

Phosphatesin solution

Weatheringof rock

Phosphatesin rock

Phosphatesin organic

compounds

Detritus

Detritivoresin soil

Phosphatesin soil

(inorganic)

Rock Precipitated(solid) phosphates

Plants

Animals

Decomposition

Runoff

To succeed on the test…1. Read the chapters.

2. Know your vocab.

3. Study the multiple choice questions in your study guide.