LIVING IN THE ENVIRONMENT 17TH MILLER/SPOOLMAN

Chapter 5

Biodiversity, Species Interactions, and Population Control

Core Case Study: Southern Sea Otters: Are They Back from the Brink of Extinction? • Habitat

• Hunted: early 1900s

• Partial recovery

• Why care about sea otters? • Ethics

• Tourism dollars

• Keystone species

Southern Sea Otter

Fig. 5-1a, p. 104

5-1 How Do Species Interact?

• Concept 5-1 Five types of species interactions—competition, predation, parasitism, mutualism, and commensalism—affect the resource use and population sizes of the species in an ecosystem.

Species Interact in Five Major Ways

• Interspecific Competition

• Predation

• Parasitism

• Mutualism

• Commensalism

Most Species Compete with One Another for Certain Resources

• For limited resources

• Ecological niche for exploiting resources

• Some niches overlap

Some Species Evolve Ways to Share Resources

• Resource partitioning

• Using only parts of resource

• Using at different times

• Using in different ways

Resource Partitioning Among Warblers

Fig. 5-2, p. 106

Fig. 5-2, p. 106

Blackburnian

Warbler

Black-throated

Green Warbler

Cape May

Warbler

Bay-breasted

Warbler

Yellow-rumped

Warbler

Cape May

Warbler

Stepped Art

Blackburnian

Warbler

Black-throated

Green Warbler

Yellow-rumped

Warbler

Bay-breasted

Warbler

Fig. 5-2, p. 106

Specialist Species of Honeycreepers

Fig. 5-3, p. 107

Fig. 5-3, p. 107

Fruit and seed eaters Insect and nectar eaters

Greater Koa-finch

Kuai Akialaoa

Amakihi

Kona Grosbeak

Crested

Honeycreeper Akiapolaau

Maui Parrotbill Apapane

Unknown finch ancestor

Most Consumer Species Feed on Live Organisms of Other Species (1)

• Predators may capture prey by

1. Walking

2. Swimming

3. Flying

4. Pursuit and ambush

5. Camouflage

6. Chemical warfare

Predator-Prey Relationships

Fig. 5-4, p. 107

Most Consumer Species Feed on Live Organisms of Other Species (2)

• Prey may avoid capture by

1. Run, swim, fly

2. Protection: shells, bark, thorns

3. Camouflage

4. Chemical warfare

5. Warning coloration

6. Mimicry

7. Deceptive looks

8. Deceptive behavior

Some Ways Prey Species Avoid Their Predators

Fig. 5-5, p. 109

Fig. 5-5a, p. 109

(a) Span worm

Fig. 5-5b, p. 109

(b) Wandering leaf insect

Fig. 5-5c, p. 109

(c) Bombardier beetle

Fig. 5-5d, p. 109

(d) Foul-tasting monarch butterfly

Fig. 5-5e, p. 109

(e) Poison dart frog

Fig. 5-5f, p. 109

(f) Viceroy butterfly mimics monarch

butterfly

Fig. 5-5g, p. 109

(g) Hind wings of Io moth resemble

eyes of a much larger animal.

Fig. 5-5h, p. 109

(h) When touched, snake

caterpillar changes shape to look

like head of snake.

(d) Foul-tasting monarch butterfly

(e) Poison dart frog

Stepped Art

(h) When touched,

snake caterpillar changes

shape to look like head of snake.

(a) Span worm (b) Wandering leaf insect

(c) Bombardier beetle

(f) Viceroy butterfly mimics

monarch butterfly

(g) Hind wings of Io moth

resemble eyes of a much

larger animal.

Fig. 5-5, p. 109

Science Focus: Threats to Kelp Forests

• Kelp forests: biologically diverse marine habitat

• Major threats to kelp forests

1. Sea urchins

2. Pollution from water run-off

3. Global warming

Purple Sea Urchin

Fig. 5-A, p. 108

Predator and Prey Interactions Can Drive Each Other’s Evolution

• Intense natural selection pressures between predator and prey populations

• Coevolution

• Interact over a long period of time

• Bats and moths: echolocation of bats and sensitive hearing of moths

Coevolution: A Langohrfledermaus Bat Hunting a Moth

Fig. 5-6, p. 110

Some Species Feed off Other Species by Living on or in Them

• Parasitism

• Parasite is usually much smaller than the host

• Parasite rarely kills the host

• Parasite-host interaction may lead to coevolution

Parasitism: Trout with Blood-Sucking Sea Lamprey

Fig. 5-7, p. 110

In Some Interactions, Both Species Benefit

• Mutualism

• Nutrition and protection relationship

• Gut inhabitant mutualism

• Not cooperation: it’s mutual exploitation

Fig. 5-8, p. 110

Mutualism: Hummingbird and Flower

Mutualism: Oxpeckers Clean Rhinoceros; Anemones Protect and Feed Clownfish

Fig. 5-9, p. 111

Fig. 5-9a, p. 111 (a) Oxpeckers and black rhinoceros

Fig. 5-9b, p. 111 (b) Clownfish and sea anemone

In Some Interactions, One Species Benefits and the Other Is Not Harmed

• Commensalism

• Epiphytes

• Birds nesting in trees

Commensalism: Bromiliad Roots on Tree Trunk Without Harming Tree

Fig. 5-10, p. 111

5-2 What Limits the Growth of Populations?

• Concept 5-2 No population can continue to grow indefinitely because of limitations on resources and because of competition among species for those resources.

Most Populations Live Together in Clumps or Patches (1)

• Population: group of interbreeding individuals of the same species

• Population distribution

1. Clumping

2. Uniform dispersion

3. Random dispersion

Most Populations Live Together in Clumps or Patches (2)

• Why clumping?

1. Species tend to cluster where resources are available

2. Groups have a better chance of finding clumped resources

3. Protects some animals from predators

4. Packs allow some to get prey

Population of Snow Geese

Fig. 5-11, p. 112

Generalized Dispersion Patterns

Fig. 5-12, p. 112

Fig. 5-12a, p. 112

(a) Clumped (elephants)

Fig. 5-12b, p. 112

(b) Uniform (creosote bush)

Fig. 5-12c, p. 112

(c) Random (dandelions)

Populations Can Grow, Shrink, or Remain Stable (1)

• Population size governed by

• Births

• Deaths

• Immigration

• Emigration

• Population change =

(births + immigration) – (deaths + emigration)

Populations Can Grow, Shrink, or Remain Stable (2)

• Age structure

• Pre-reproductive age

• Reproductive age

• Post-reproductive age

Some Factors Can Limit Population Size

• Range of tolerance

• Variations in physical and chemical environment

• Limiting factor principle

• Too much or too little of any physical or chemical factor can limit or prevent growth of a population, even if all other factors are at or near the optimal range of tolerance

• Precipitation

• Nutrients

• Sunlight, etc

Trout Tolerance of Temperature

Fig. 5-13, p. 113

Fig. 5-13, p. 113

Lower limit

of tolerance

Higher limit

of tolerance

No

organisms

Few

organisms Abundance of organisms

Few

organisms

No

organisms

Po

pu

lati

on

siz

e

Zone of

physiological

stress

Optimum range Zone of

physiological

stress

Zone of

intolerance

Low Temperature High

Zone of

intolerance

No Population Can Grow Indefinitely: J-Curves and S-Curves (1)

• Size of populations controlled by limiting factors: • Light

• Water

• Space

• Nutrients

• Exposure to too many competitors, predators or infectious diseases

No Population Can Grow Indefinitely: J-Curves and S-Curves (2)

• Environmental resistance

• All factors that act to limit the growth of a population

• Carrying capacity (K)

• Maximum population a given habitat can sustain

No Population Can Grow Indefinitely: J-Curves and S-Curves (3)

• Exponential growth

• Starts slowly, then accelerates to carrying capacity when meets environmental resistance

• Logistic growth

• Decreased population growth rate as population size reaches carrying capacity

Logistic Growth of Sheep in Tasmania

Fig. 5-15, p. 115

Fig. 5-15, p. 115

2.0 Population

overshoots

carrying

capacity

Carrying capacity

1.5

Population recovers

and stabilizes

Nu

mb

er

of

sh

eep

(m

illi

on

s)

.5

Exponential

growth

Population

runs out of

resources

and crashes

1.0

1800 1825 1850 1875 1900 1925

Year

Science Focus: Why Do California’s Sea Otters Face an Uncertain Future?

• Low biotic potential

• Prey for orcas

• Cat parasites

• Thorny-headed worms

• Toxic algae blooms

• PCBs and other toxins

• Oil spills

Population Size of Southern Sea Otters Off the Coast of So. California (U.S.)

Fig. 5-B, p. 114

Case Study: Exploding White-Tailed Deer Population in the U.S.

• 1900: deer habitat destruction and uncontrolled hunting

• 1920s–1930s: laws to protect the deer

• Current population explosion for deer

• Spread Lyme disease

• Deer-vehicle accidents

• Eating garden plants and shrubs

• Ways to control the deer population

Mature Male White-Tailed Deer

Fig. 5-16, p. 115

When a Population Exceeds Its Habitat’s Carrying Capacity, Its Population Can Crash

• A population exceeds the area’s carrying capacity

• Reproductive time lag may lead to overshoot

• Population crash

• Damage may reduce area’s carrying capacity

Exponential Growth, Overshoot, and Population Crash of a Reindeer

Fig. 5-17, p. 116

Fig. 5-17, p. 116

2,000 Population

overshoots

carrying

capacity

1,500 Population

crashes

1,000

500 Carrying

capacity

Nu

mb

er

of

rein

deer

1910 1920 1930 1940 1950

0

Year

Species Have Different Reproductive Patterns (1)

• Some species

• Many, usually small, offspring

• Little or no parental care

• Massive deaths of offspring

• Insects, bacteria, algae

Species Have Different Reproductive Patterns (2)

• Other species

• Reproduce later in life

• Small number of offspring with long life spans

• Young offspring grow inside mother

• Long time to maturity

• Protected by parents, and potentially groups

• Humans

• Elephants

Under Some Circumstances Population Density Affects Population Size

• Density-dependent population controls

• Predation

• Parasitism

• Infectious disease

• Competition for resources

Several Different Types of Population Change Occur in Nature

• Stable

• Irruptive • Population surge, followed by crash

• Cyclic fluctuations, boom-and-bust cycles • Top-down population regulation

• Bottom-up population regulation

• Irregular

Population Cycles for the Snowshoe Hare and Canada Lynx

Fig. 5-18, p. 118

Fig. 5-18, p. 118

160

140 Hare

Lynx

100

120

80

60

Po

pu

lati

on

siz

e (

tho

usan

ds)

20

40

1845 1855 1865 1875 1885 1895 1905 1915 1925 1935

0

Year

Humans Are Not Exempt from Nature’s Population Controls

• Ireland

• Potato crop in 1845

• Bubonic plague

• Fourteenth century

• AIDS

• Global epidemic

5-3 How Do Communities and Ecosystems Respond to Changing Environmental

Conditions?

• Concept 5-3 The structure and species composition of communities and ecosystems change in response to changing environmental conditions through a process called ecological succession.

Communities and Ecosystems Change over Time: Ecological Succession

• Natural ecological restoration

• Primary succession

• Secondary succession

Some Ecosystems Start from Scratch: Primary Succession

• No soil in a terrestrial system

• No bottom sediment in an aquatic system

• Takes hundreds to thousands of years

• Need to build up soils/sediments to provide necessary nutrients

Primary Ecological Succession

Fig. 5-19, p. 119

Fig. 5-19, p. 119

Balsam fir, paper birch,

and white spruce forest

community

Jack pine, black spruce, and aspen Heath mat Small herbs

and shrubs Lichens and mosses

Exposed rocks

Balsam fir, paper birch, and white spruce forest community

Jack pine, black spruce, and aspen Heath mat

Small herbs and shrubs Lichens and

mosses Exposed rocks

Stepped Art

Fig. 5-19, p. 119

Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (1)

• Some soil remains in a terrestrial system

• Some bottom sediment remains in an aquatic system

• Ecosystem has been

• Disturbed

• Removed

• Destroyed

Natural Ecological Restoration of Disturbed Land

Fig. 5-20, p. 120

Fig. 5-20, p. 120

Mature oak and hickory forest

Shrubs and small pine seedlings

Young pine forest with developing understory of oak and hickory trees

Perennial weeds and grasses

Annual weeds

Annual weeds

Mature oak and hickory forest Young pine forest

with developing understory of oak and hickory trees

Shrubs and small pine seedlings Perennial

weeds and grasses

Stepped Art

Fig. 5-20, p. 120

Secondary Ecological Succession in Yellowstone Following the 1998 Fire

Fig. 5-21, p. 120

Some Ecosystems Do Not Have to Start from Scratch: Secondary Succession (2)

• Primary and secondary succession • Tend to increase biodiversity • Increase species richness and interactions among species

• Primary and secondary succession can be interrupted by • Fires • Hurricanes • Clear-cutting of forests • Plowing of grasslands • Invasion by nonnative species

Science Focus: How Do Species Replace One Another in Ecological Succession?

• Facilitation

• Inhibition

• Tolerance

Succession Doesn’t Follow a Predictable Path

• Traditional view

• Balance of nature and a climax community

• Current view

• Ever-changing mosaic of patches of vegetation

• Mature late-successional ecosystems

• State of continual disturbance and change

Living Systems Are Sustained through Constant Change

• Inertia, persistence

• Ability of a living system to survive moderate disturbances

• Resilience

• Ability of a living system to be restored through secondary succession after a moderate disturbance

• Some systems have one property, but not the other: tropical rainforests

Three Big Ideas

1. Certain interactions among species affect their use of resources and their population sizes.

2. There are always limits to population growth in nature.

3. Changes in environmental conditions cause communities and ecosystems to gradually alter their species composition and population sizes (ecological succession).