Bio 100 Chapter 38

Chapter 38Community and

Ecosystem Ecology

Lecture Outline

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Ridding the World of Waste

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38.1 Competition can lead to resource partitioning

Competition is rivalry between populations for the same resources, such as light, space, nutrients, or mates

Competitive Exclusion Principle – no two species can occupy the same niche at the same time

Ecological niche – the role organism plays in its community, including its habitat (where the organism lives) and its interactions with other organisms and the environment

Resource partitioning – decreases competition between the two species

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Figure 38.1A Competition only occurs between two species of

Paramecium when they are grown

together

When one species fed on the bottom and the other fed

on suspended food, resource

partitioning occurred and competition decreased

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P.aurelia grownseparately

P.caudatum grownseparately

Both species grown together

Time

Po

pu

lati

on

Den

sit

yP

op

ula

tio

nD

ens

ity

Po

pu

lati

on

Den

sit

y

Figure 38.1C Niche specialization occurs among five species of coexisting warblers

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Black-throatedgreenwarbler

Cape Maywarbler

Bay-breastedwarbler

Blackburnianwarbler

Yellow-rumpedwarbler

38.2 Predator-prey interactions affect both populations

Predation occurs when one organism (the predator) feeds on another (the prey)

Predator – Prey interactions affect both populations Numbers of one species dictates numbers of the

other species

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Figure 38.2A Predator-prey interaction between a snowshoe hare and a lynx

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Nu

mb

er

(th

ou

sa

nd

s)

© Alan Carey/PhotoResearchers, Inc.

140

120

harelynx

100

80

60

40

20

1845 1855 1865 1875 1885 1895 1905 1915 1925 1935


Prey Defenses

Prey Defenses Camouflage – ability to blend into the background

http://www.youtube.com/watch?v=3WHUTL4fujo

Warning coloration tells the predator that the prey is potentially dangerous

Mimicry – when one species resembles another that possesses a defense Batesian mimicry-a mimic lacks the defense of the organism it

resembles Mullerian mimicry-species have the same defense and

resemble each other38-8

http://www.youtube.com/watch?v=3WHUTL4fujo

Figure 38.2B Antipredator defenses

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Camouflage© Gustav Verderber/Visuals Unlimited

Figure 38.2B Antipredator defenses (Cont.)

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© Zig Leszczynski/Animals Animals

Warning coloration

Viceroy

Monarch

Figure 38.2C Mimicry: All of these insects have the same coloration

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(flower fly,longhorn beetle, yellow jacket): © Edward S. Ross; (bumblebee): © James H.Robinson/Photo Researchers, Inc.

flower fly longhorn beetle

bumble bee yellow jacket

Parasitism

Parasitism – a parasite infects a host

A symbiotic relationship – at least one of the species is dependent on the other

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Commensalism

Commensalism is a symbiotic relationship between two species in which one species is benefited and the other is neither benefited nor harmed

Example: Spanish moss grow in the branches of trees, where they receive light, but they take no nourishment from the trees

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Figure 38.4 A clownfish living among a sea anemone’s tentacles

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Mutualism

Mutualism – symbiotic relationship in which both members benefit

Example: Bacteria in the human intestinal tract acquire food, but they provide us with vitamins

Relationship between plants and their pollinators is a good example of mutualism

Mycorrhizae & Lichens38-20

Figure 38.5B Cleaning symbiosis occurs when small fish clean large fish

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Cleaning symbiosis – symbiotic relationship in which crustaceans, fish, and birds act as cleaners for a variety of vertebrate

clients

Large fish in coral reefs line up at cleaning

stations and wait their turn to be cleaned by

small fish that even enter the mouths of the large

fish

Primary & Secondary Succession

Ecological Succession – series of species replacements in a community following a disturbance (flood, tornado, volcanic eruption, fire, clear-cutting forest)

Primary succession occurs in areas where no soil is present. Can take thousands of years.

Secondary succession begins in areas where soil is present. Much shorter time span than primary succession.

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Figure 38.6A Primary succession begins on areas of bare rock.Secondary succession begins at the grass stage

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b brock lichens/mosses grass low shru

secondary succession

primary succession

high shru shrub-tree low tree high tree

38.7 Ecosystems have biotic and abiotic components

Abiotic (nonliving) components: Sunlight, inorganic nutrients, type of soil, water,

temperature, wind

Biotic (living) components: Producers, consumers, scavengers (detritus feeders),

decomposers

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Autotrophs

Biotic Components of an Ecosystem

Autotrophs

Called producers because they produce food

Photoautotrophs, also called photosynthetic organisms, produce most of the organic nutrients for the biosphere

Exs: Algae, green plants

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Heterotrophs & Decomposers

Heterotrophs need a preformed source of organic nutrients Called consumers because they consume food Herbivores are animals that graze directly on plants or algae Carnivores feed on other animals Omnivores feed on both plants & animals Scavengers (detritus feeders) feed on the dead remains of

animals and plants that have recently begun to decompose Detritus refers to organic remains in the water and soil that are

in the final stages of decomposition Bacteria and fungi, including mushrooms, are the decomposers

that use their digestive secretions to chemically break down dead organic matter

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Figure 38.8A Energy flow and chemical cycling in an ecosystem

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solarenergy heat

producers

inorganicnutrient pool

consumers

heat

heat decomposersenergy

nutrients

Figure 38.8B Energy balances for an herbivore

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Heat toenvironment

Energy tocarnivores

Energyto detritus

feeders

growth and reproduction

© George D. Lepp/Photo Researchers, Inc.

Food Webs & Food Chains

Food web, a diagram that describes trophic (feeding) relationships, common in nature

Trophic Levels Diagram that shows a single path of energy flow in an

ecosystem are called Food Chain (rare in nature)

Trophic level is composed of organisms that occupy the same position within a food web or chain

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Figure 38.9 Grazing food web (top) and detrital food web (bottom)

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1

3

3

4

Autotrophs Herbivores/Omnivores Carnivores

owls

hawksbirdsnuts

leaf-eatinginsects

deer

skunks

snakes

mice

detritus

rabbitschipmunks

mice

death

deathdeath

fungi and bacteria in detritus invertebrates shrewssalamanderscarnivorous invertebrates

3

leaves

2

5foxes

38.10 Ecological pyramids are based on trophic levels

Ecological pyramid

10% rule – only about 10% of the energy of one trophic level is available to the next trophic level because of energy loss

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Figure 38.10 This ecological pyramid based on the biomass content of bog populations could also be used to

represent an energy pyramid

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top carnivores1.5 g/m2

carnivores11g/m2

herbivores37g/m2

autotrophs809 g/m2

38.12 The phosphorus cycle

Phosphorus On land, the very slow weathering of rocks places phosphate

ions in the soil Some of these become available to plants, which use phosphate

to make ATP, and nucleotides that become DNA and RNA

Human Activities and the Phosphorus Cycle Human beings boost the supply of phosphate by mining

phosphate ores for producing fertilizer and detergents Results in eutrophication (overenrichment) of waterways

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Figure 38.12 The phosphorus cycle

38.13 The nitrogen cycle

Ammonium (NH4+) Formation and Use

Nitrogen fixation occurs when nitrogen gas (N2) is converted to ammonium (NH4

+), a form plants can use Cyanobacteria and bacteria living on some roots can fix

atmospheric nitrogen

Formation of Nitrogen Gas Denitrification is the conversion of nitrate back to nitrogen gas,

which then enters the atmosphere Denitrifying bacteria living in the anaerobic mud of lakes, bogs, and

estuaries carry out this process as a part of their own metabolism

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38.13 The nitrogen cycle is gaseous

Human Activities and the Nitrogen Cycle Humans significantly increase transfer rates in nitrogen cycle by

producing fertilizers from N2

Nearly doubles the fixation rate Fertilizer, which also contains phosphate, runs off into lakes and

rivers and results in an overgrowth of algae and rooted aquatic plants

Acid deposition occurs because nitrogen oxides (NOx) and sulfur dioxide (SO2) enter the atmosphere from the burning of fossil fuels Combine with water vapor to form acids that eventually

return to the Earth

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Figure 38.13 The nitrogen cycle

38.14 The carbon cycle

Human Activities & the Carbon Cycle

More CO2 is being deposited in the atmosphere than is being removed due to burning of fossil fuels and destruction of forests to make way for farmland

Greenhouse gas – allows solar radiation to pass through but hinder the escape of heat back into space, called the greenhouse effect

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Figure 38.14 The carbon cycle

Connecting the Concepts:Chapter 38

Competition leads to resource partitioning Prey use various defenses against predators 3 examples of symbiotic relationships Primary vs. Secondary Ecological Succession Trophic levels exist within food chains & food

webs (10% energy conservation between levels) Nutrients cycle (Phosphorous, Nitrogen &

Carbon)

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Bio 100 Chapter 38