UNIT 13Chapter 50: An Introduction to Ecology & the Biosphere

Chapter 51: Behavioral Biology

Chapter 52: Population Ecology

Chapter 53: Community Ecology

Chapter 54: Ecosystems

Chapter 55: Conservation Biology

Ecology is the scientific study of the interactions between organisms and their environment

Introduction

Ecologists make predictions of what should be observed in the environment

Environment of any organism includes the following components:– Abiotic factors: non-living chemical and physical

factors (temperature, light, water, and nutrients)– Biotic factors: the living components

Organismal: behavioral and physiologicalways individualsinteract with theenvironment

Levels of Ecology

Population: a population is a group of individuals of the same species living in a particular geographic area– Population ecology examines factors that affect

population size and composition

Community:a community consistsof all the organisms ofall the species thatinhabit a particulararea– Community ecology

examines the interactionsbetween populations predation, competition,

and disease

Ecosystem: an ecosystem consists of all the abiotic factors in addition to the entire community of species that exist in a certain area– Ecosystem ecology:

energy flow cycling of chemicals

Climate is the prevailing weather conditions in an area– Temperature, water, light, and wind are major

components of climate

Climate determines the makeup of biomes– Major types of ecosystems

Ex. Desert, tundra, tropical rain forest, grassland, etc.

Temperature & Water

Annual means for temperature and rainfall are reasonably well correlated with the biomes we find in different regions

The tropics between 23.5° north latitude and 23.5° south latitude experience the least seasonal variation and have the highest biodiversity

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Introduction

Ethology is the study of how animals behave in their natural environment

Behavior results from both genes and environment Innate behaviors are fixed, the result of genetics

Learning

Learning is based on experience and results in modification of behavior Maturation: changes resulting from growth

and development Habituation: desensitization to unimportant

stimulus

Imprinting is a short period of learning early in life Usually involves

young recognizing (and becoming attached to) parents

Konrad Lorenz experimented with geese

Classical conditioning is a type of associative learning Animals learn to associate one stimulus

with another Ivan Pavlov experimented with dogs

Ring bell and spray powdered meat in their mouths caused salivation

Eventually, the bell alone caused salivation

Operant conditioning involves trial and error Association with a punishment or reward

Cognition

Cognition is the ability to perceive, store, process and use information from sensory receptors Kinesis: change in activity based on

random behavior Taxis: movement/orientation based on a

stimulus Migration: long-distance movements that

occur regularly

Organism Interactions

Social behavior is any interaction between animals (usually the same species) Agonistic: conflict, usually no harm done Dominance hierarchies: involve ranking of

individuals Alpha organism dominates group

Courtship consists of behaviors that lead to copulation Monogamous – strong bond between male

and female Polygamous – multiple mates exist

Polyandry – female with multiple males Polygyny – male with multiple females

Promiscuous – no lasting bond between males and females

Inclusive Fitness

Most social behaviors are selfish, but some involve helping others Altruism decreases

individual fitness, but increases fitness of group

Related individuals will often help each other survive and/or reproduce Kin selection: individuals help relatives

raise young

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IntroductionIntroduction

A A populationpopulation is a group of the same is a group of the same species that inhabit the same general species that inhabit the same general areaarea

DensityDensity and and distributiondistribution are influenced are influenced by organisms’ interactions with the by organisms’ interactions with the environmentenvironment

Survivorship CurvesSurvivorship Curves

DemographyDemography is the study of the factors is the study of the factors that control the growth and decline of that control the growth and decline of populationspopulations– Survivorship curvesSurvivorship curves reflect births and deaths reflect births and deaths

in a populationin a population Curve types: Type I, Type II, Type IIICurve types: Type I, Type II, Type III

Population GrowthPopulation Growth

The The exponential modelexponential model reflects unlimited reflects unlimited resources for growthresources for growth

The The logistic modellogistic model incorporates limiting incorporates limiting factors into population growthfactors into population growth– NN is the number of individuals is the number of individuals– Carrying capacityCarrying capacity ( (KK) is the maximum ) is the maximum

number of individuals that can be supported number of individuals that can be supported naturallynaturally

Two basic types of species exist based on Two basic types of species exist based on reproductive traitsreproductive traits– K selectionK selection

organisms live/reproduce around Korganisms live/reproduce around K– Long maturation, long lifespan, low deathrate, few Long maturation, long lifespan, low deathrate, few

offspring, several reproductions in lifeoffspring, several reproductions in life

– r selectionr selection populations fluctuate well below Kpopulations fluctuate well below K

– Short maturation, short lifespan, high deathrate, Short maturation, short lifespan, high deathrate, many offspring, one reproductionmany offspring, one reproduction

Limiting factors Limiting factors fall into two categoriesfall into two categories– Density dependentDensity dependent

factors increase their pressure as population factors increase their pressure as population growsgrows

type of negative feedbacktype of negative feedback

– Density independentDensity independent factors unrelated to population size, no feedbackfactors unrelated to population size, no feedback

Negative feedback prevents unlimited Negative feedback prevents unlimited population growthpopulation growth

Some populations go through regular Some populations go through regular “boom and bust” cycles“boom and bust” cycles– Common with predator/prey interactionsCommon with predator/prey interactions

Age structureAge structure is the relative number of is the relative number of individuals at each ageindividuals at each age

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Introduction

• A community is a collection of species living closely enough for potential interaction

• Interspecific interactions involve relationships between species

• An organism’s niche is its biotic and abiotic requirements from its environment• Its role in the environment• Organisms with identical niches cannot coexist

(competitive exclusion principle)

Interspecific Interactions

• Competition, mutualism, commensalism and predation (parasitism) are examples of interspecific interactions

• Predator/prey interactions have “forced” evolution to develop ways to protect prey species from their predators• Coloring, camouflage, toxins, mechanical

defenses, etc.• Herbivory is a type of predation

• Coloration and camouflage are frequently used by nature to aid prey avoid being eaten• Cryptic coloration – traditional camouflage,

deceptive markings• Aposematic coloration – warning colors to

indicate the presence of a toxin• Batesian mimicry – a harmless species

resembles a harmful one• Müllerian mimicry – two (or more) “dangerous”

species have evolved to resemble one another

Trophic Structure

• Food chains and food webs are used to trace the path of energy-containing carbon compounds

Disturbance & Succession

• Disturbances affect community structure and stability• Stability is the ability of a community to persist

• Events like fire, weather, natural disasters and human activity can disturb a community• Some events are routine, while others occur

randomly• Usually considered to have a negative impact,

but actually necessary for development and survival

• Humans are the most widespread source of disturbance and it usually results in a decrease in species diversity

• Succession is the sequence of changes that occur after a disturbance• Primary succession – occur in a lifeless area

• Soil needs to be created first by mosses and lichens

• Secondary succession – occur when an area is cleared by an event

• Soil still exists, grasses and small shrubs grow

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Trophic Relationships

• Trophic relationships involve the cycling of carbon in an ecosystem• Primary producers

are photosynthetic• All consumers

depend on photosynthetic output

• Amount of light energy converted to chemical energy in a given time period is called primary production• Ecosystems vary in their productivity

Primary Production

• Amount of chemical energy converted into a consumer’s biomass is secondary production

Secondary Production

• Joules (J) are unit of energy

• Trophic efficiency is typically ~10%• Amount of energy passed to next trophic

level

• Trophic efficiency has important implications for humans

• Human activity disrupts biogeochemical cycles• Nutrients removed from one part of

biosphere and placed in another

Human Impact

• Agriculture and eutrophication

• Acid precipitation threatens plants and aquatic organisms• Caused by burning fossil fuels

• Toxins introduced into a food web become more concentrated in successive trophic levels• Biological

magnification

• Human activities were depleting atmospheric ozone (O3)• Ozone protects

Earth from UV radiation

• Use of CFC’s is likely cause

• Climate change occurs due to rising CO2 levels in the atmosphere• Greenhouse

effect causes global warming

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