Download Population Growth Rate

Chapter 3 Communities, Biomes
and Ecosystems
1. Life in a community


Every ecosystem has a tendency to change
from simple to complex. A final , stable
community will become established ( climax
community)
What grows and survives varies…
Limiting Factors

Factors that affect an organism’s ability to
survive in its environment.

(any condition that keeps the size of a population
from increasing)

May be abiotic or biotic

Fig. 3.1 trees at timberline
Tolerance

All organisms have a
range of tolerance for
different conditions.
Tolerance

Ability to withstand fluctuations in A or B
Factors.
Ecological Succession

2 kinds:


Primary
Secondary
Ecological Succession

Change in the composition of species that make up a
community over time.

Orderly

Natural

Occurs in stages

Can take decades or centuries
2. Types of Ecological Succession

1. Primary succession

The collinization of barren land.
Primary Succession

“First life”—On barren rock or ice.


Such as : newly formed volcanic island.; sand
dune
First org. to establish

Pioneer Species

Often are Lichens

(bacteria +fungus, OR algae + fungus)
Lichens
Pioneer Species

First plants on Barren rocks.

Lichens, small plants with
brief life cycles

Improve conditions.
Primary Succession continued…
Soil develops gradually
 grasses overtake the
lichens; then ferns; then
shrubs and trees.
 Eventually the land
is colonized by plants
that become the main
vegetation.
..The Climax
Community

Succession
2. Secondary Succession
Occurs after:
existing community
cleared by a
disturbance.
Occurs where
the soil is intact
For example:
following a fire
Secondary
Eventually…


A stable community is established.—a Climax
Community
Influenced by 2 factors
Temperature

And
Rainfall
Climax Community

Stable array of species that persists relatively
unchanged over time.
Stages of Secondary Succession
Forests
warm surface current
cold surface current
dry
warm temperate
subpolar
tropical
cool temperate
polar (ice)
cold
Fig. 44.6, p. 760
Biomes

Terrestrial

Aquatic
 Marine


Estuary
Freshwater
3.2 Terrestrial Biomes

Climate results from uneven heating


Latitude




The average weather conditions in an area
More direct sunlight at equator
Elevation
Ocean currents
Land masses
Major Terrestrial Biomes

Characterized by Latitude and Climate


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
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



Tundra
Boreal Forest (Tiaga) (pine trees)
Temperate Forest ( deciduous trees)
Temperate woodland and shrubland ( example: chaparrel)
Temperate Grassland
Desert
Tropical Savanna
Tropical Dry ( Seasonal) Forest
Tropical Rain Forest
Tundra



The tundra is cold year-round—it has short cool
summers and long, severe winters. Drainage is poor
permafrost
little precipitation, about 4 to 10 inches per year, and
what it does receive is usually in the form of snow or
ice. There is little diversity of species. Plant life is
dominated by mosses, grasses, and sedges
Tundra

Below polar ice caps

Treeless

Permafrost

Shallow-rooted vegetation

Plants are low, cushiony mats

lichens

Cold and dark most of the year
A,b arctic; c is alpine
Fig. 44.19, p. 771
Boreal Forest (Taiga)




Below Tundra
Pine trees
Short, moist summers
Moose, deer
The Taiga

Also know as boreal forests, the taiga is dominated by
conifers (cone-bearing plants), most of which are
evergreen (bear leaves throughout the year). The
taiga has cold winters and warm summers.

The soil is acidic and mineral-poor. It is covered by
a deep layer of partially-decomposed conifer needles.
Temperate Deciduous Forest
Four distinct seasons
Hot in the summer to below freezing in the winter.
Rain is plentiful
Deciduous trees -drop their leaves in the autumn,



Broad-leaf deciduous trees
4 seasons—hot summers, cold winters
Deer, rabbits, squirrels, oak trees, maple trees
Tropical Rain Forest




Warm, uniform temps
Large amounts of rain throughout the year ( 125660 cm/yr)
Vertically layered
epiphytes
Tropical rainforest

Highest species diversity (species rich

Amazon rainforests produce about
40% of the world's oxygen
One in four pharmaceuticals comes from a plant in
the tropical rainforests


Tropical Rainforest



Plants grow rapidly /use up nutrients.
 This results is a soil that is poor.
The tropical rainforest is Dense/not much sunlight reaches the
forest floor.
Adaptations





Specialized roots help hold up plants in the shallow soil
some plants climb on others to reach the sunlight
smooth bark and smooth or waxy flowers speed the run off
of water
plants have shallow roots to help capture nutrients from the
top level of soil.




Grassland
Extremely rich soil
b/c grasses die off annually
Well-suited to agriculture

“The Breadbasket of the World”
2 General Kinds
Temperate Grassland




Fertile soil
Thick cover of grasses
No trees
Maintained by periodic fires and animal
grazing
Tropical Savanna




Grasses and Scattered Trees
Africa, s. America, Australia
Hot & rainy summers
Winters- cool & dry
Deserts

All continents except Europe

Annual rate of evaporation exceeds rate of
precipitation

Less than 26 centimeters annual rainfall

One third of land surface

Nocturnal animals

Plants adapted
Desert

Some plant adaptations:.
 Some plants, called succulents, store water in their
stems or leaves;
 Long root systems.
 Waxy coating on stems and leaves help reduce
water loss.

Flowers that open

Nocturnal animals

Aquatic Ecosystems




Grouped based upon abiotic factors
Freshwater
Transitional
marine
Freshwater



Rivers & Streams
Water movement varies
More plants where water is slow

Fish feed here
Lakes & ponds

Bodies of standing freshwater

Temperature varies with season

So does: oxygen & nutrients

Highest in Autumn and Spring
Transition Aquatic Ecosystems

Estuary
Estuary

Partially enclosed area where saltwater and freshwater
mix

High species diversity

Important spawning area and “nurseries”

Dominated by salt-tolerant plants-algae, seaweed, marsh
grass

Lots of waterfowl feed and migrating

Examples are Chesapeake Bay, San Francisco Bay, salt
marshes of New England
Marine Biomes

Zonation


Photic Zone
Aphotic Zone
Marine Biomes


Estuaries
Effects of Tides

Intertidal Zone
Animal adaptations here
In the Light
In the Dark
Alpine Tundra

Occurs at high elevations throughout the world

No underlying permafrost

Plants are low, cushions or mats as in arctic
tundra
Chapter 4: Population Biology


How do populations grow?
What factors inhibit the growth of populations
4.1 Population Dynamics—
Learning Objectives

Population Dynamics


What is a population?
Compare patterns of Population growth


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

2 Models
1. Exponential Growth—the J-curve
2. Logistic Growth-The S-Curve
Describe life-history pattern and compare this to
graphic representations :
Be able to make predictions as to the effect of
environmental factors on population growth.

How fast do populations grow?
Population Growth Rate


How Fast the population is growing
2 most important





Birth Rate: Natality
Death Rate: Fatality
also
Immigration
Emigration
Exponential Growth




Unchecked growth
When no limits are put on the growth rate
J-shaped Curve
All populations grow at this rate until some
limiting factor slows the growth rate.
Exponential Growth
Fastest rate of growth, under ideal conditions.
 Unchecked Growth

Initially slow, then speeds up and remains
rapid.
 The larger the population becomes, the faster it
grows!
 J-Curve (if graphed the rate)


Examples: Houseflies, Bacteria
Exponential Growth—unlimited
resources
Exponential growth: J-Curve:
The larger the population gets, the faster it
grows.
Aphids—plentiful food,
room.
What limits population growth?
Limiting Factors:
food, predation, disease, lack of space

Carrying Capacity

Maximum # of a species an environment supports
indefinitely.


Logistic Growth: S-shaped curve
Pop. growth rate slows or stops at
the population’s carrying
capacity.
carrying
capacity
Occurs when number of births is
less than deaths OR when
emigration exceeds immigration.
Time
Copy this picture into your notes,
including labeling.
(“K” is usually used to reference
“carrying capacity”
Reproductive Pattern

Reproductive pattern


Determines a population’s growth.
2 generalized patterns


rate-strategy ( r-strategy)
K-strategy
Reproductive Patterns

R-Strategy –Rate Strategists

This is an adaptation to living in where fluctuations in biotic
or abiotic factors occurs




Example: mosquitoes
Changeable or unpredictable environments.
Populations are controlled by Density-Independent factors
Organism’s characteristics:





Small body size
Short life span
Mature rapidly
Reproduce early
Large numbers of offspring

Few survive
K-Strategists




Live in predictable environments
So, the carrying capacity of the environment changes little
from year to year.
Example: elephants and most large mammals, trees
Organism’s characteristics:



Stable environment
Slow rate of reproduction
Produce few offspring





Many survive
Offspring mature slowly
Care for their young
Maintain pop. sizes at or near carrying capacity
Populations controlled by Density-dependent factors
Population Dispersal Patterns

The pattern of spacing of individuals within an
area.

3 main patterns of dispersal


Uniform: black bears ( territorial); fish-schools
(safety & good for predation)
Clumped: Most common pattern


herds of grazing animals, such as American Bison
Random: dandelions
How organisms are dispersed
clumped most common
Population Density

The NUMBER of individuals in a given area.
2 Kinds of Limiting Factors related
to dispersal patterns.

1. Density-dependent Factors


Often biotic factors
Exert a greater influence the larger the population
gets.


EX: disease, parasites, competition, predators
2. Density Independent Factors


Affect a population regardless of their density
Most are abiotic factors

Ex: Volcano, temperature, storms

..\Bio 1\World Population.htm
1999
1975
domestication of plants,
animals 9000 B.C. (about
11,000 years ago)
agriculturally based
urban societies
beginning of industrial,
scientific revolutions
Fig. 40.9, p. 695
Chapter 5: Biodiversity and
Conservation




Biodiversity
Genetic diversity
Species diversity
Ecosystem diversity
Dead as a Dodo



Flightless bird that lived on
the island of Mauritius
Killed off by Europeans
Once the dodo was extinct,
a tree native to Mauritius
stopped reproducing
Biodiversity & Extinction

90 percent of all species that have ever lived are
now extinct

Biodiversity is greater than ever

Current range of biodiversity is the result of past
extinctions and recoveries
Importance of Biodiversity
5.2 Threats to Biodiversity

Extinction Rates

Background Extinction

Mass Extinctions
Humans and
Mammalian Diversity

Humans began hunting mammals about 2 million
years ago

About 11,000 years ago, they began to drastically
reduce mammalian habitats

Of the 4,500 living mammal species, 300 (6.7
percent) are endangered




Extinction
Endangered Species
Threatened
Introduced Species
Endangered Species

An endemic species that is extremely
vulnerable to extinction

Endemic means a species originated in one
geographic region and is found nowhere else
Threatened Regions
Critically endangered species
Threatened species
Relatively stable species;
populations intact
Factors that Threaten Biodiversity

Habitat Loss—Number one





Tropical Rain Forest
Coral Reefs
Overexploitation
Habitat Fragmentation
Pollution



Biological Magnification
Acis Precipitation
Eutrophication (cultural)
DDT in Food Webs

Synthetic pesticide banned in
the United States since
1970s.

Top carnivore birds
accumulated DDT in their
tissues.
Shells are soft, crack, babies die.
DDT banned in US in 1972!
Habitat Loss: Threats to Coral
Reefs

Natural threats, such as hurricanes

Man-made threats

Water pollution, oil spills

Dredging

Dynamite and cyanide fishing

Coral bleaching
Habitat Loss

In the U.S.:

98 percent of tallgrass prairies are gone

50 percent of wetlands have been destroyed
Coral Bleaching

Reef-building corals have photosynthetic,
dinoflagellate symbionts

When stressed, corals expel the protistans

If the stress persists, the coral will die, leaving only
its bleached hard parts behind

Coral bleaching may be an effect of global warming
and increased sea temperatures
Habitat Fragmentation


Habitats are chopped up into patches
Three effects:



Increases habitat edges
Decreases number of individuals that can be supported;
may be too few to allow breeding
Decreases the area in which individuals can find food or
other resources
Habitat Degradation
Introduced Species

Species that have been introduced into a habitat

either deliberately or accidentally

No natural enemies or controls

Can outcompete native species

Play a role in 70 percent of cases where endemic species
are threatened
Nile Perch in East Africa

Nile perch were introduced into Lake Victoria as a
food source

This predator ate native cichlids; drove many species
to extinction

Now Nile perch species is close to crashing
Rabbits in Australia

Rabbits were introduced for food and hunting

Without predators, their numbers soared

Attempts at control using fences or viruses have thus
far been unsuccessful
Kudzu in Georgia

Imported for erosion control

No natural herbivores, pathogens, or competitors

Grows over landscapes and cannot be dug up or
burned out

May turn out to have some commercial use
5.3 Conservating Biology
Rachel Carson

Oceanographer and marine biologist

Published Silent Spring in 1962

Described the harmful effects of pesticides on
songbirds and other species

Book helped launch the environmental movement
Conservation Biology

Systematic study of biodiversity

Works to elucidate the evolutionary and ecological
origins of biodiversity

Attempts to identify ways to maintain biodiversity for
the good of human populations
Density-Dependent Controls

Logistic growth equation deals with densitydependent controls

Limiting factors become more intense as
population size increases

Disease, competition, parasites,
of waste products
toxic effects
Density-Independent Controls

Factors that affect population growth regardless of
population density.

Natural disasters or climate changes affect large and small
populations alike
Age Structure Diagrams

Show age distribution of a population
RAPID GROWTH
SLOW GROWTH
ZERO GROWTH NEGATIVE GROWTH
Pollutants

Substances with which an ecosystem has had
no prior evolutionary experience.

No adaptive mechanisms are in place to deal
with them
Air Pollutants

Carbon oxides

Sulfur oxides

Nitrogen oxides

Volatile organic compounds

Photochemical oxidants

Suspended particles
Industrial Smog

Gray-air smog

Forms over cities that burn large amounts of coal and
heavy fuel oils; mainly in developing countries

Main components are sulfur oxides and suspended
particles
Photochemical smog

Brown-air smog

Forms when sunlight interacts with components from
automobile exhaust

Nitrogen oxides are the main culprits

Hot days contribute to formation
Thermal Inversion

Weather pattern in which a layer of cool, dense
air is trapped beneath a layer of warm air
cool air
warm inversion air
cool air
Acid Deposition

Caused by the release of
sulfur and nitrogen
oxides

Coal-burning power
plants and motor vehicles
are major sources
Ozone Thinning

In early spring and
summer ozone layer
over Antarctica thins

South
America
Seasonal loss of
ozone is at highest
level ever recorded
Antarctica
Effect of Ozone Thinning

Increased amount of UV radiation reaches
Earth’s surface

UV damages DNA and negatively affects human
health

UV also affects plants, lowers primary
productivity
Protecting the Ozone Layer

CFC production has been halted in developed
countries, will be phased out in developing countries

Methyl bromide will be phased out

Even with bans it will take more than 50 years for
ozone levels to recover
Generating Garbage

Developed countries
generate huge amounts
of waste

Paper products account
for half the total volume

Recycling can reduce
pollutants, save energy,
ease pressure on landfills
Land Use



Almost 21 percent of Earth’s land is used for
agriculture or grazing
About half the Earth’s land is unsuitable for such
uses
Remainder could be used, but at a high
ecological cost
Green Revolutions

Improvements in crop production

Introduction of mechanized agriculture and practices
requires inputs of pesticides, fertilizer, fossil fuel

Improving genetic character of crop plants can also
improve yields
Deforestation

Removal of all trees from large tracts of land

38 million acres logged each year

Wood is used for fuel, lumber

Land is cleared for grazing or crops
Effects of Deforestation

Increased leaching and soil erosion

Increased flooding and sedimentation of
downstream rivers

Regional precipitation declines

Possible amplification of the greenhouse effect
Regions of Deforestation

Rates of forest loss are greatest in Brazil, Indonesia,
Mexico, and Columbia

Highly mechanized logging is proceeding in
temperate forests of the United States and Canada
Reversing Deforestation

Coalition of groups dedicated to saving Brazil’s
remaining forests

Smokeless wood stoves have saved firewood in India

Kenyan women have planted millions of trees
Destroying Biodiversity

Tropical rainforests have the greatest variety of
insects, most bird species

Some tropical forest species may prove valuable
to humans

Our primate ancestors evolved in forests like the
ones we are destroying
Desertification

Conversion of large tracts of grassland to
desertlike conditions

Conversions of cropland that result in more than
10 percent decline in productivity
The Dust Bowl

Occurred in the 1930s in the Great Plains

Overgrazing and prolonged drought left the ground
bare

1934 winds produced dust storms that stripped about
9 million acres of topsoil
Ongoing Desertification

Sahel region of Africa is undergoing rapid
desertification

Causes are overgrazing, overfarming, and prolonged
drought

One solution may be to substitute native herbivores
for imported cattle
Water Use and Scarcity

Most of Earth’s water is too salty for human
consumption

Desalinization is expensive and requires
large energy inputs

Irrigation of crops is the main use of freshwater
Negative Effects of Irrigation

Salinization, mineral buildup in soil

Elevation of the water table and waterlogging

Depletion of aquifers
Ogallala Aquifer

Extends from southern South Dakota to central Texas

Major source of water for drinking and irrigation

Overdrafts have depleted half the water from this
nonrenewable source
Water Pollutants







Sewage
Animal wastes
Fertilizers
Pesticides
Industrial chemicals
Radioactive material
Excess heat (thermal pollution)