r 4 population ecology - mrs. neill's...

4 Population Ecology C

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Chapter 4

TOPIC

POPULATION ECOLOGY

Indicator Species Serve as Biological Smoke Alarms

• Indicator species • Provide early warning of damage to a community

• Can monitor environmental quality

• Trout

• Birds

• Butterflies

• Frogs

Case Study: Monteverde Golden Toad

• INDICATOR SPECIES

• Golden toads lived in Costa Rica’s Monteverde cloud forest.

• Golden toads were first described in 1964. They were extinct by 1989.

• WHY??

• Drier days – pools and ponds dried up – nowhere to lay eggs

• Warming Oceans – cloud elevation higher drying out the rainforest

• Warmer nights – increased growth of fungi that infected the frog skin

• What other factors may cause frog extinction??

Talk About It Why is the extinction of the

golden toad a global concern?

Case Study: Why Are Amphibians Vanishing? (1)

• Habitat loss and fragmentation

• Prolonged drought

• Pollution

• Increase in UV radiation

• Parasites

• Viral and fungal diseases

• Climate change

• Overhunting

• Nonnative predators and competitors

Case Study: Why are Amphibians Vanishing? Fast Track pg 97

Frogs serve as indicator species because different parts of their life cycles can be easily disturbed.

Figure 7-3

• Many Costa Rican frogs are so specialized, that they have learned to survive in the canopies of trees by using the water that's deposited in bromeliads and tree trunks; this way, they don't have to descend to the ground and risk being attacked by predators or of their tadpoles being eaten by fish.

• Tropical frogs are probably one of the most sensitive animals in the world and react very rapidly to substantial changes in their environments.

• They also form vital parts of the ecosystems to which they belong.

• That is why they are considered "an indicator species" - the species that "indicate" the state of the health of their ecosystems.

• The frogs' disappearance could cause loss of control over some populations of insects and could let them grow in numbers, or it could be the cause of reduction in the quantity of food for other forest animals feeding on frogs etc.

Tropical Rain Forests Are Disappearing

• Cover about 2% of the earth’s land surface

• Contain about 50% of the world’s known plant and animal species

• Disruption will have three major harmful effects • Reduce biodiversity

• Accelerate global warming

• Change regional weather patterns

Levels of Ecological Organization

• The study of how organisms interact with each other and with their environments

• Scientists study ecology at various levels of organization.

Lesson 4.1 Studying Ecology

Smallest unit of a chemical element

that exhibits its chemical properties Atom

Molecule Chemical combination of two or

more atoms of the same or different

elements

Cell

The fundamental structural and

functional unit of life

Organism An individual living being

Population A group of individuals of the same

species living in a particular place

Community Populations of different species

living in a particular place, and

potentially interacting with each

other

Stepped Art

Ecosystem A community of different species

interacting with one another and with

their nonliving environment of matter

and energy

Biosphere Parts of the earth's air,water, and soil

where life is found

Oxygen Hydrogen

Water

Fig. 3-5, p. 58

Biotic and Abiotic Factors

• Biotic factors: Parts of an

ecosystem that are living or

used to be living

• Abiotic factors: Parts of an

ecosystem that have never

been living Water Air Nutrients Rocks Heat Solar energy


Did You Know? Decaying

organisms are biotic factors

as long as their structure

remains cellular.

Major Biotic and Abiotic Components of an Ecosystem

Fig. 3-6, p. 59

Habitat

• The specific environment in which an organism lives

• Habitats provide an organism with resources—anything an organism needs to survive and reproduce, including food, shelter, and mates.


Lesson 4.2 Describing Populations

From 1900 to 2000, the white-tailed deer population of New York state grew from about 20,000 to more than 1 million. Densities of more than 100 deer per sq mi occur in some metropolitan areas.

Population Size


• The number of individuals in a population at a given time

• Sudden and dramatic decreases in population size can

indicate an unhealthy population headed toward

extinction.

• Ecologists often use sampling

techniques to estimate

population size.

Did You Know? The passenger pigeon

was once North America’s most abundant

bird. Hunting drove them to extinction in

less than 100 years.

Counting Laysan Albatross Nests

Population Density


• Measure of how crowded a population is

• Larger organisms

generally have lower

population densities.

• Low population density:

More space, resources;

finding mates can be difficult

• High population density:

Finding mates is easier; tends to be more

competition; more infectious disease; more

vulnerability to predators

Northern pintail ducks

Population Distribution Lesson 4.2 Describing Populations

• How organisms are arranged within an area:

• Random distribution:

Organisms arranged in

no particular pattern

• Uniform distribution:

Organisms evenly spaced

• Clumped distribution:

Organisms grouped near resources;

most common distribution in nature

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Generalized Dispersion Patterns

Fig. 5-12, p. 112

Fig. 8-2a, p. 162 (a) Clumped (elephants)

Why clumping???

•Resources a species

needs vary greatly in

availability

• Protection from

predators

• Gives predatory species

a better success rate

when hunting

• Temporary groups for

mating and care of young

Fig. 8-2b, p. 162 (b) Uniform (creosote bush)

Why uniform

distribution?

• Usually found when

resources are scare but

evenly spread out over an

area

• Helps to reduce

intraspecific competition

over scarce resources

Fig. 8-2c, p. 162 (c) Random (dandelions)

Why random???

• Rarely occurs in

nature.

• Will only occur

when resources are

fairly high and

spread out over a

large area.

Age Structure


• Relative

number

of

organisms

of each age

group within

population

• Can be

used to

predict

future

population

growth of a

population

Sex Ratios


• Proportion of males to females

• Age structure diagrams give information about sex ratios.

• For a monogamous species, the ideal sex ratio is 50:50.

Lesson 4.3 Population Growth

From 1800 to today, the human population has grown from about 1 billion to more than 6.8 billion—an exponential rate of increase.

Populations Can Grow, Shrink, or Remain Stable

• Population size governed by • Births

• Deaths

• Immigration

• Emigration

• Population change =

(births + immigration) – (deaths + emigration)

Immigration and Emigration


• In addition to births and deaths, population growth is

affected by immigration and emigration—individuals

moving into and out of a population.

• Migration, seasonal movement into and out of an area,

can temporarily affect

population size.



Calculating Population Growth


• Determined by the following equation:

(birthrate + immigration rate) – (death rate + emigration rate)

• Growing populations have a positive growth rate; shrinking

populations have a negative growth rate.

• Usually expressed in terms of individuals per 1000

Did You Know? Immigration contributes more than 1 million people to the U.S. population per year.

Biotic Potential


• An organism’s maximum ability

to produce offspring in ideal

conditions

• Many factors influence biotic

potential, including gestation

time and generation time.

• Organisms with high biotic

potential can recover more

quickly from population declines

than organisms with low biotic

potential.

Birth and Death Rates Lesson 4.3 Population Growth

• A population’s relative

birth and death rates

(mortality and natality)

affect how it grows.

• Survivorship curves

show how the

likelihood of death

varies with age.



• The way to represent the age structure of a population is with a survivorship curve.

• Late loss population live to an old age.

• Constant loss population die at all ages.

• Most members of early loss population, die at young ages.

Species Have Different Reproductive Patterns Type III

• Some species

• Many, usually small, offspring

• Little or no parental care

• Massive deaths of offspring

• Insects, bacteria, algae

Species Have Different Reproductive Patterns Type I

• 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

Age

Early loss

Late loss

Logistic Growth and Limiting Factors


• Growth almost always slows and

stops due to limiting factors.

• Limiting factors:

Environmental

characteristics

slow population growth

and determine carrying

capacity.

• Density-dependent:

Influence changes with

population density.

• Density-independent:

Influence does not change with population density.

Under Some Circumstances Population Density Affects Population Size

• Density-dependent population controls • WAR – DISEASE - FAMINE

• Predation

• Parasitism

• Infectious disease

• Competition for resources

Exponential Growth


• Population increases by

a fixed percentage

every year.

• Normally occurs only

when small populations

are introduced to an

area with ideal

environmental conditions

• Rarely lasts long



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