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Inquiry into LifeEleventh Edition

Sylvia S. Mader

Chapter 33Lecture Outline

Prepared by: Wendy VermillionColumbus State Community College

Copyright The McGraw-Hill Companies, Inc. Permission required for reproduction or display.

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33.1 Scope of ecology

• Ecological terms– Ecology- study of interactions of organisms with other organisms

and with the physical environment– Modern ecology encompasses levels of study

• Organism- the level of individual

• Population-all members of same species inhabiting an area

• Community- all populations in an area

• Ecosystem-a community and its physical environment

• Biosphere-all communities on Earth

– Ecological succession- a change in community composition over time

– Climax community- associated with a particular geographical area

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Levels of organization in a coral reef

• Fig. 33.1

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Scope of ecology cont’d.

• Ecological succession– Occurs after a disturbance

• Primary succession occurs in areas where there is no soil

• Secondary succession occurs when there is soil available

– Pioneer species- the first to come in and colonize in secondary succession

– Succession proceeds through stages as illustrated on the following slide

• The slide illustrates terrestrial succession

• Succession also occurs in aquatic communities

– Bodies of fresh water proceed through stages and are eventually filled in by sediments

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Secondary succession in a forest

• Fig. 33.2

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Scope of ecology cont’d.

• Models of succession– Climax-pattern model-particular areas will always lead to a

specific climax community• Based on the fact that climate determines what plants survive• Exact composition of climax community need be the same

– For example, the climax community in an area may be deciduous forest, but the tree species may differ

– Facilitation model-each successive community prepares the environment for the next

• Grasses are necessary before shrubs, and then shrubs before trees

– Inhibition model-colonizing species hold on to space until they die or are damaged

– Tolerance model-different species can colonize at the same time• Random chance determines which arrives first

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33.2 Patterns of population growth

• Patterns of population growth– Biotic potential- highest rate of per capita increase

• Depends upon:

– Usual number of offspring per reproduction

– Chances of offspring surviving until reproduction

– How often each individual reproduces

– Age at which reproduction begins

– Exponential growth• Graphing number of organisms against time gives a J-shaped curve

– Lag phase-slow growth period because population is small

– Exponential growth phase-accelerates and population exhibits biotic potential

– Continues until environmental resistance occurs

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Patterns of population growth cont’d.

• Patterns of growth cont’d.– Logistic growth

• Produces an S-shaped curve

• Population growth levels off when environmental resistance is met

– Lag phase-slow growth, population is small

– Exponential growth phase-accelerated growth, biotic potential

– Deceleration phase-population growth slows down

– Stable equilibrium phase-little growth takes place because birth rate and death rate are about equal

» Occurs at carrying capacity of environment

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Patterns of population growth

• Fig. 33.4

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Patterns of population growth cont’d.

• Survivorship– Growth curves assume all individuals are identical

• In real life, individuals are in different life stages

– Cohort-group of individuals born at the same time• Plotting the number surviving over time gives us a survivorship

curve

– Type I survivorship curve- most individuals survive until old age• Ex: humans

– Type II- survivorship curve- decreases consistently over time• Ex: songbirds

– Type III survivorship curve- most individuals die early• Ex: oysters

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Survivorship curves

• Fig. 33.5

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Patterns of population growth cont’d.

• Human population growth– Doubling time- length of time it takes for population to double its

numbers– Currently is 53 years– Has rapidly increased

• 1st billion didn’t occur until 1800

• 2nd billion in 1930

• 3rd billion in 1960

• Current population is over 6 billion

– Must double food, water, energy, jobs just to maintain current standard of living

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World population growth

• Fig. 33.6

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Patterns of population growth cont’d.

• More-developed versus less-developed countries– MDC’s

• Population growth is low and standard of living high

• Increased rapidly between 1850 and 1950 due to decreased death rate

• This was followed by a decrease in birth rate-demographic transition

• Has stabilized at 0.1%

• Germany, Hungary, Italy, Greece, Sweden-actually decreasing in size

– U.S.- no leveling off

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Patterns of population growth cont’d.

• MDC’s versus LDC’s cont’d.– LDC’s

• Population growth is expanding rapidly and standard of living is low

• Population of LDC’s could reach 11 billion by 2100

– Most of this increase in Latin America, Africa, and Asia

• Ways to decrease this expected growth are

– Establish/strengthen family planning programs

– Use social progress to reduce desire for large families

– Delay onset of childbearing

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World population growth

• Fig. 33.6

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Patterns of population growth cont’d.

• Age distributions– Divide populations into 3 groups- dependency, reproductive, and

post reproductive• Many MDC’s have a stable age structure

– If every couple has 2 children, this results in replacement reproduction

» Replacement reproduction can eventually lead to zero population growth

• LDC’s have a younger population so they can be expected to continue to grow

– The faster replacement reproduction is achieved, the sooner zero population growth will result

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Age-structure diagrams (1998)

• Fig. 33.7

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33.3 Regulation of population growth

• Types if life history patterns– Opportunistic pattern

• Small size, mature early, short life span• Offspring are small, many produced with little paternal care

– Greater numbers increase likelihood some will survive a population crash

• colonizers

– Equilibrium pattern• Size of population remains around carrying capacity• Resources are scarce; those who compete successfully will have

the most offspring• Large size, slow to mature, long life span• Specialists instead of colonizers• Become extinct if normal way of life is destroyed

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Regulation of population growth cont’d.

• Life history patterns cont’d.– Density-independent factors-abiotic factors such as weather,

natural disasters• Populations with opportunistic life-history pattern tend to be

controlled by density-independent factors

– Density-dependent factors-biotic factors such as predation, parasitism, competition

• Populations with equilibrium life-history pattern tend to be controlled by density-dependent factors

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Life history patterns

• Fig. 33.8

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Regulation of population growth cont’d.

• Competition– Occurs when members of 2 different species try to utilize the

same resource– Competitive exclusion principle-no 2 species can occupy the

same ecological niche at the same time• Ecological niche-role organism plays in the community; includes

habitat, resources used, and interactions

– Resource partitioning• Slight differences in the way a resource is utilized

• Decreases competition

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Competition between two laboratory populations of Paramecium

• Fig. 33.9

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Competition between two species of barnacles

• Fig. 33.10

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Regulation of population growth cont’d.

• Predation– Predator-prey population dynamics

• Cycling of predator and prey populations

• Occurs when either predators overkill prey, or when prey overuse resources and their numbers crash

– In either case, predator numbers also decrease from a decrease in food source

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Predator-prey interaction between a lynx and a snowshoe hare

• Fig. 33.11

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Regulation of population growth cont’d.

• Antipredator defenses– Coevolution-two species respond to selective pressure imposed

by the other• Predator species evolve strategies to get maximum amount of food

with the least expenditure of energy• Prey species evolve strategies to escape predation

– Mimicry-one species resembles another that has an antipredator defense

• Can help predator catch food or a prey species avoid capture• Batesian mimicry-a species that lacks a defense mechanism mimics

another that has if– Ex: nonstinging insects with black and yellow color like wasp

• Mullerian mimicry-several species with the same defense mechanism share a common characteristic

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Antipredator defenses

• Fig. 33.12

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Mimicry

• Fig. 33.13

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Regulation of population growth cont’d.

• Symbiosis-interactions between members of 2 populations– Parasitism- parasite derives nourishment from host

• Parasite benefits and the host is harmed

– Commensalism-one species benefits and the other is neither harmed nor benefited

– Mutualism- both species benefit

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Egret symbiosis

• Fig. 33.14

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Cleaning symbiosis

• Fig. 33.15