esc 301.02 ii ecology a short

7/29/2019 Esc 301.02 II Ecology a Short

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ESC 301

ECOLOGY-Part A

Ferhan een


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What is Ecology?

Ecology is the study of populations,

communities, and ecosystems

Hierarchy of Ecology

biosphere

ecosystem

community population

individual


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Organisms

Made of cells

Eukaryotic vs. Prokaryotic Species

Groups of organisms that resemble

one another in appearance,behavior, and genetic make up

Populations

Communities Ecosystems

Biosphere

Biosphere

Biosphere

Ecosystems

Communities

Populations

Organisms


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Biotic communities: grouping or

assemblage of plants, animals, andmicrobes

Species: different kinds of plants, animals,and microbes in the community

Populations: number of individuals that

make up the interbreeding, reproducinggroup


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EVOLUTION AND ECOLOGY

DNA

Gene

Mutation

Natural Selection

Fitness

Speciation


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How does evolution actually

work?

Natural Selection

Mutation

-natural

-mutation caused by X-rays and mutagenic

chemicals


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Mechanisms of Species Adaptation Change through natural selection

Selective pressure determines which organisms survive

and reproduce and which are eliminated.


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Natural SelectionDarwin, 1859:

He observed that the Galpagos species differed from each

other in beak size and shape. He also noted that the beak

varieties were associated with diets based on different

foods. He concluded that when the original South

American finches reached the islands, they dispersed to

different environments where they had to adapt to

different conditions. Over many generations, they changedanatomically in ways that allowed them to get enough food

and survive to reproduce.


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Natural selection works as follows:

Within a species there are always slight differences between

individuals. Some individuals may have characteristics which make

them better able to survive than others (they are better adapted).

These individuals are likely to live longer, breed and produce more

offspring. If the characteristic which helped the parent survive is

passed on to the offspring there will be more individuals with this

character.

After several generations individuals with the favorable character

will be the most common.

Over a long period of time new varieties and species can evolve.

If environmental conditions change different characteristics may

be favored and selected.


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EXAMPLE:RESISTANCE

DEVELOPMENT

IN INSECTS


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An example of evolution resulting from natural selection was

discovered among "peppered" moths living near English

industrial cities.

During the 19th century, sooty smoke from coal burning

furnaces killed the lichen on trees and darkened the bark. Onthese trees and other blackened surfaces, the dark colored ones

were harder to spot by birds who ate them and, subsequently,

they more often lived long enough to reproduce. Over

generations, the environment continued to favor darkermoths. As a result, they progressively became more

common. By 1895, 98% of the moths in the vicinity of English

cities like Manchester were mostly black.

NATURAL SELECTION:

EXAMPLE OF MOTH


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Dark moths on light

colored bark areeasy targetsfor hungry birds,

but are

hidden on pollutiondarkened trees.

NATURAL SELECTION:

EXAMPLE OF MOTH


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Since the 1950's, air pollution controls have significantly reduced

the amount of heavy particulate air pollutants reaching the

trees, buildings, and other objects in the environment. As a

result, lichen has grown back, making trees lighter in color. In

addition, once blackened buildings were cleaned making them

lighter in color. Now, natural selection favors lighter moth

varieties so they have become the most common.

NATURAL SELECTION - EXAMPLE OF MOTH


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The Limits of Change

Adapt

Move (migrate)

Die (extinction)

Extinction

Biodiversity = Speciation- Extinction


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Adaptations to the Environment


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Vulnerability of different organisms to

environmental changes


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EVOLUTION OF EARTH


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The evolution of life is linked to the physicaland chemical evolution of the Earth.

primitive bacteria (3.5 billion years ago)

evolution of photosynthetic prokaryotes (2.3 billion years

ago) release of oxygen into ocean and atmosphere

evolution of oxygen-using organisms

evolution of more complex organisms including humans.


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EVOLUTION OF LIFE


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Populations are groups intermating individuals.

Population ecology is the study of interactions withinpopulations (i.e., intraspecific interactions).

We can characterize individual populations in terms of

Size (average vs. variation) Density (& impacts on size; density dependence)

Patterns of Dispersion

Demographics (age structure, sex ratios) Rates of growth (or decline)

Limits on population growth

Populations


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Population Growth

example:

10,000 birds in a population 1500 births and 500 deaths per year

1500/10,000 - 500/10,000 = .10 or 10%

expressed by saying there is a 10% increase per bird peryear


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Growth of Populations

Factors affecting population growthBiotic Potential

Environmental Resistance

Density-dependent factors

Density-independent factors

Survivorship

Age Structure


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Biotic Potential and Environmental

Resistance


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Environmental resistance: combination of biotic and abiotic factors thatmay limit population increase

Predators, competitors, disease

Adverse weather, limited food/nutrients

Factors of environmental resistance are either:

density-independent: effect does not vary with population density;e.g., adverse weather

density-dependent: effect varies with population density; e.g.,infectious disease

Critical number: the lowest population level for survival and recovery


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Idealized models describe two kinds of

population growth1. exponential growth

2. logistic growth

How do populations grow?


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A J-shaped growth curve, described by the

equation G = rN, is typical of exponential

growth G = the population growth rate

r = the intrinsic rate of increase, or an organism's

maximum capacity to reproduce

N = the population size


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0 5 10 15 20

0

500

1000

1500

Time (years)

Popu

lation

size

r=0.

06

r=0.02

r = 0

r = -0.05

high intrinsic

rate of increase

low intrinsic

rate of increase

zero population

growth

negative intrinsic

rate of increase


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K= carrying capacity

The term

(K

-N

)/K

accountsfor theleveling

off of thecurve

)K

NK.(N.r

t

NG

=

=

Logistic growthThe growth is slowed by population-limiting factors


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Population Growth Curves


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Population Growth Curves

Reproductive strategies:

Many offspring withlow parental care

Few offspring withhigh parental careJ-shaped growth curve

S-shaped growth curve


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Survivorship

mirrors mortality

expressed in survivorship curves

plots surviving individuals at different age groups

three types of survivorship curves late loss (Type I)

constant loss (Type II)

early loss (Type III)


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Survivorship Curves


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Age Structure DiagramsAge

% males in the

age group

% females in the

age group

Post-reproductive

Reproductive

Pre-reproductive Younge

rtoolder


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What Does the Age Structure Diagram Indicate?

Growth Patterns

Proportional Distribution in Age Categories

Expanding

Stabilizing

Diminishing

Three general types of age structure diagrams:

Th t t f l ti i th ti f


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RAPID GROWTH

Kenya

Male Female

Percent of population Percent of population Percent of population

SLOW GROWTH

United States

Male Female

ZERO GROWTH/DECREASE

Italy

Male Female

Ages 45+

Ages 1544

Under15

Under15

Ages 45+

Ages 1544

The age structure of a population is the proportion of

individuals in different age-groups


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The concept of nicheHabitat niche

Trophic or food niche

Multidimensional niche

Habitat- The place where an organism lives.Examples: A lions habitat is a savanna. A monkeys

habitat is a rain forest. A cactuss habitat is in the desert.

Niche - An organisms way of life; occupation.

Example: A lions niche includes where and how it finds

shelter and food, when it reproduces, how it relates to

other animals


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Communities

Grouping or assemblage of plants,

animals, and microbes

Factors influencing Species Diversity in anEcosystem

The Edge Effect

Latitude

Human Influences


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The Edge Effect


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Law of Limiting Factors

Compare the

tolerancedifferences for atrout and a catfishusing water: temperature (cold or

warm). oxygen concentration

(high or low).

salinity (high or low).


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The Competitive Exclusion Principle


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Symbiosis

Mutualism: + and + = Both species benefitby the interaction between the twospecies: yucca plant and Pronuba moth

Commensalism: + and 0 = One speciesbenefits from the interaction and theother is unaffected: remora fish and shark

Parasitism

Predatorprey dynamics

Introduced species

OTHER INTERSPECIFIC RELATIONSHIPS


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PredatorPrey Balance: Wolves and Moose


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POPULATIONS AND COMMUNITIES ARE DYNAMIC

Absence of natural enemies allows a

herbivore population to exceed carryingcapacity, which results in overgrazing of thehabitat.

The herbivore population subsequentlycrashes.

The size of the herbivore population is

maintained so that overgrazing or otheroveruse does not occur.


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PlantHerbivore Dynamics

No regulatory control

(predation) onherbivores

Went into exponential

growth pattern Overgrazed habitat

Massive die-off of

herbivores

Reindeer on St. Matthew Island


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Species Introduction: Rabbits in Australia

Introduced into Australia from England in

1859 No natural enemies rabbit population

exploded

Overabundant herbivore populationdevastated natural vegetation

Using disease ( a virus) as a control measure

killed first 97-99 % of population , butincreased the resistance in the long-term.


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Principles ofpopulation ecology may be usedto

manage wildlife, fisheries, and forests for sustainable yield reverse the decline of threatened or endangered species

reduce pest populations

IPM = Integrated Pest Management Integrated pest management (IPM) uses a combination of

biological, chemical, and cultural methods to controlagricultural pests.

IPM relies on knowledge of the population ecology of thepest its associated predators and parasites crop growthdynamics.

Where is this information used?

esc 301.02 ii ecology a short

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