Chapter 4: Ecosystems and Communities

Section 4.1 Climate

What is Weather?• Weather can change on a day to day basis

What is climate?

• Defined by year after year patterns

What is a microclimate?

● When Environmental conditions change over small distances

What shapes climate?

• Solar energy trapped in the biosphere

• Latitude

• Transport of heat by winds and ocean currents

What is the relationship between Solar energy and the greenhouse effect?

How does latitude affect amount of solar energy hitting Earth? • At the poles solar

energy is spread over a larger area due to the Earth’s curvature

• Earth’s surface can be divided into 3 zones

• Polar• Temperate• Tropical

• Amount of solar energy varies throughout the year

How does Heat transport in the Biosphere relate to winds?• Winds are caused the

rising and cooling of air• Warm air is less dense and

rises

• Cold air is denser and sinks

• Winds transport heat from warm to cold air

• Earth’s rotation leads to general west to east movement over temperate zone

How do Ocean current effect heat transport in the Biosphere?

• Surface waters are moved by winds

• Currents transport large amounts of heat

• Affect weather of nearby landmasses

• Depp ocean currents cause by sinking in polar regions,

• This water rises in upwellings in warmer areas

Niches and community interactions

Section 4.2

What is a niche?

• Each species has a range of conditions under which it can grow and reproduce

• Help define where and how an organism can live

What does tolerance mean in Biology?

• Every species has it’s own tolerance range

• A species tolerance for environmental conditions helps define it’s habitat

• Example environmental conditions are temperature, amount of sunlight

How do you define a niche?

• A niche describes not only what an organism does, but how it interacts with biotic and abiotic factors in the environment

• A niche is:• The range of physical and biological conditions in

which a species lives

• & the way the species obtains what it need to survive and reproduce

• Understanding a nice is important to understanding how organisms interact to form a community

What is a resource?

• Can refer to anything necessary for life

• Examples are:• Water• Nutrients• Light• Food • Space• Shelter• Places to feed

Physical aspects of niches

• Part of an organisms niche involves abiotic factors that are required for survival

• Amphibians loose and absorb water through their skin

• They must live somewhere moist• If too hot and dry, or too cold most

won’t survive for long

Biological aspects of niches

• Part of an organism's niche involve biotic factors required for survival

• When/how it reproduces• Food source• How it obtains food

• Example, birds on Christmas Island in Indian ocean live in harmony, but prey on different fish

When do organisms compete against each other? • When organisms attempt to use the same limited ecological resource

• Can occur within the same species - intraspecific

• Can occur between different species – interspecific

• Basis of survival of the fittest!

What is the competition exclusion principle?

• No two species can occupy exactly the same niche in exactly the same habitat

• One species will always be better at competing for limited resources

• It is very rare for natural resources to overlap

Are organisms any good at sharing?

• Species often divide resources rather than compete for them

• North American warblers all live harmoniously in the same tree

• Resources for each species are similar but different

• Competition helps determine the number and kinds of species in a community, and the niche each species occupies

What is the relationship between Predator and Prey populations?• Predators can affect the

size of the prey population in an ecosystem

• Predators can determine places prey can live and feed

Do you see a similar relationship between herbivores and plants? • Just as important as

predator – prey relationships

• Herbivores can affect the size and distribution of plant populations

• Can determine the places that certain plants can live

What is a Keystone species?• Changes in the amount of a single species

can cause dramatic change• Off pacific coast of USA Sea otters eat

urchins• Urchins are herbivores and eat kelp (a type

of giant algae)• When otters were nearly eliminated by

hunting the kelp forest nearly disappeared• Too many urchins devoured all the kelp• Other organisms which lived on kelp died• When otters given protected status,

everything started to return to normal, but now otter numbers are falling again

• Wolves in Yellowstone national park another perfect example of keystone species

What does Symbioses mean?

• Any relationship where two creatures live closely together

• 3 types of symbiotic relationships• Mutualism• Parasitism • Commensalism

What is mutualism?

• Nile crocodile and Egyptian plover bird

• The bird will clean the crocodile's mouth as it basks in the sun

• There is a clear benefit to both organisms

• Both consent to the ”relationship”

What is Parasitism?

• Where one organism lives inside or on another organism

• Often weakens but not does kill the host

• Obtain all or part of their nutritional needs from the host

• Is the giraffe and the tickbird an example of parasitism or mutualism?

What is Commensalism?

• A relationship in which one organism benefits and another is neither helped nor harmed

SuccessionSection 4.3

What happened at Krakatau?

• In 1883, an explosive eruption destroyed the island of krakatau

• Within 2 years grasses were growing

• Within 14 years there were 49 plant species

• By 1929 there were 300 plant species

• Now there is a forest!

What is Ecological Succession?

• A series of predictable changes that occur over time

• Over the course of succession the number of species will increase

• Causes – volcanic eruption, glacier retreating

What do these plants have in common?

• Pioneer species – the first to colonize an area of land• Simple structure• Often get crowded out over time

Secondary succession

• Pre existing soil speeds up the development process

Why does succession occur?

• Organisms change the environment they live in

• As organic matter begins to accumulate it becomes easier for more complex plants to grow

• Trees for example will provide shade and cooler temperatures for other species

• Roots will help soil build up• Help organisms to find their niche

What is a climax community?

• End stage of succession

• Not always stable and uniform

• Succession doesn’t always follow the same path

Succession after natural disasters

• In a healthy ecosystem secondary succession will return the land to the original climax community

• Example – Coral reef or tropical rainforest recovering from a storm

• Often climax communities are not stable

• Patchwork of different areas in different stages of secondary succession

Do Human’s disrupt the sequence of succession?

• Ecosystems may or may not recover from human disturbances

• Microclimate and soil can be changed so much that the original community cannot return

Patterns of succession….

• We learn from experience

• Identify predictable stages based on our experiences

• For example compare what happened with Mt St Helens with records of Krakatau

Writing exercise

• What effect do pioneer species have on an environment undergoing primary succession

BiomesSection 4.4

Why do Oregon, Montana and Vermont have different climates

• Proximity to oceans, & Mountain ranges will affect regional climate

How do mountains affect amount of rain on land?

• Could be Oregon, could be North West England

• Same process

Biomes• At least 10 groups of regional climate communities – Biomes• Biomes can be described in terms of abiotic factors like climate and soil

type, and biotic factors such as plant and animal life• Examples are

• Tropical rain forest• Grassland/savana• Desert• Temperate grassland• Temperate woodland• Temperate forest• Tundra

Climate diagrams – what kind of environment do these two graphs correspond to?

• Left = temperate forest

• Right = desert

Biomes of the world

Comparing biomes

• What is the difference between desert and tundra? Where do you find each of them in the world?

• What is the difference between tropical rain forests and tropical dry forests? Where do you find each of them in the world?

• What is the difference between temperate grassland and temperate forest? Where do you find each of them

Section 4.5Aquatic Ecosystems

What factors affect life in aquatic ecosystems?

Water depth

Temperature

Flow

Amount of dissolved nutrients

What is the photic zone?

• The sunlit region near the surface in which photosynthesis can occur• Can range in depth from 200m to a few

meters• Phytoplankton (photosynthetic algae)

live in the photic zone• Zooplankton eat phytoplankton

• Aphotic zone - where photosynthesis can not occur

• Benthic zone - sediments at rocks at base of water• Highly variable depending on water depth

How do temperature and nutrient availability affect life in aquatic ecosystems?

• Aquatic habitats are warmer near the equator can colder near the poles

• Temperature also varies with depth

• Currents can have large effects on ocean temperature; drastically changing typical water temperatures for a given place

• Nutrients are often scarce, and availibility will have large effects on ecosystem

What are the three main types of freshwater ecosystems?

• Rivers/Streams: Often lots of oxygen but little plant life near source

• Lakes/Ponds: Food webs based around plants and algae

• Freshwater Wetlands: Water either covers soil or present near the surface part of the year

• Help purify water , and prevent flooding • Examples: Bogs, marheses and

swamps

What is an estuary? Why are they so important?

• A special kind of wetland where a river meets the sea• Therefore they are a mixture of freshwater

and seawater• Also affected by tides

• Shallow - photosynthetic benthic zone• Large amount of biomass

• Acts as spawning/nursery ground for ecologicall and comerically important fish

• Key examples - salt marsh and mangrove swamp

How is the ocean classified? • The ocean is divided into zones based on the depth and distance

from the shore

How do creatures live in such extreme environments?

• Total darkness, High pressure and frigid temperatures lead to some weird adaptations

• Life revolves around chemosynthesis and hydrothermal vents rather than photosynthetic organisms