BIODIVERSITY, SPECIES BIODIVERSITY, SPECIES INTERACTIONS, and INTERACTIONS, and POPULATION CONTROL! POPULATION CONTROL!

How do Species Interact?How do Species Interact?

5 major ways!5 major ways! Interspecific CompetitionInterspecific Competition PredationPredation ParasitismParasitism MutualismMutualism CommensalismCommensalism Interactions help limit population size. These Interactions help limit population size. These

interactions influence abilities of interacting interactions influence abilities of interacting species to survive and reproduce; thus serving species to survive and reproduce; thus serving as agents of natural selection. as agents of natural selection.

CompetitionCompetition

Each species has a niche.(some are Each species has a niche.(some are generalists with broad niches, generalists with broad niches, others are specialists with narrow others are specialists with narrow niches)niches)

When niches overlap, competition When niches overlap, competition occurs. No two species can share a occurs. No two species can share a niche for very long (competitive niche for very long (competitive exclusion principle)exclusion principle)

PREDATORS! PREDATORS!

In predation, a member of one species In predation, a member of one species feeds directly upon all or part of another feeds directly upon all or part of another living organism as part of a food web.living organism as part of a food web.

Herbivores, carnivores, and omnivores are Herbivores, carnivores, and omnivores are predators. (Decomposers and detritovores predators. (Decomposers and detritovores are not)are not)

See page 102 to read about how predators See page 102 to read about how predators catch prey and how prey tries to keep from catch prey and how prey tries to keep from being eaten. Vivid reading! being eaten. Vivid reading!

PREY!! PREY!! PREDATOR!!PREDATOR!!

Read about Kelp! p. 104Read about Kelp! p. 104

PARASITISM! (Feeds on the PARASITISM! (Feeds on the body or energy of another body or energy of another organism)organism)

MUTUALISM! Both MUTUALISM! Both Benefit!Benefit!

Commensalism!Commensalism!Benefits one, but Benefits one, but doesn’t help or harm other. (bromeliads doesn’t help or harm other. (bromeliads and tree….whale and barnacle)and tree….whale and barnacle)

Reduce Competition by Reduce Competition by Resource Partioning! Resource Partioning!

Species competing for similar scarce Species competing for similar scarce resources evolve specialized traits resources evolve specialized traits that allow them to use shared that allow them to use shared resources at different times, in resources at different times, in different ways, or in different places. different ways, or in different places.

Examples are warblers and honey Examples are warblers and honey creepers. creepers.

We all live in the same tree! We all live in the same tree! But we eat different things But we eat different things in different places in our in different places in our tree!tree!

Limits to Population Limits to Population Growth!! Growth!!

Populations differ in factors such as distribution, Populations differ in factors such as distribution, numbers, age structure, and density. numbers, age structure, and density.

Age structure(number of individuals in different Age structure(number of individuals in different age groups)age groups)

Density(number of individuals in a certain space)Density(number of individuals in a certain space) Population dynamics is a study of how these Population dynamics is a study of how these

characteristics of populations change in response characteristics of populations change in response to environmental conditions.(Temperature, to environmental conditions.(Temperature, presence of disease or harmful chemicals, presence of disease or harmful chemicals, resource availability, and arrival or disappearance resource availability, and arrival or disappearance of a competitor)of a competitor)

Snow bird to beach bunny! (NY to Snow bird to beach bunny! (NY to FLA) (Mice leave when cat moves FLA) (Mice leave when cat moves in)in)

CLUMPS and PATCHESCLUMPS and PATCHES

Most populations live in clumps or patches. Most populations live in clumps or patches. (Desert vegetation near water, wolf packs, (Desert vegetation near water, wolf packs, fish schools, bird flocks, herds)fish schools, bird flocks, herds)

Groups cluster where resources areGroups cluster where resources are Searching in groups is better than aloneSearching in groups is better than alone Groups protected more from predatorsGroups protected more from predators Better hunting in packsBetter hunting in packs Group together for mating and raising Group together for mating and raising

young.young. The Living World is Clumpy and Patchy!!The Living World is Clumpy and Patchy!!

We are happy! We We are happy! We Clump! Clump!

Uniform RandomUniform RandomDispersion Dispersion DispersionDispersion

4 Variables Govern 4 Variables Govern Population Size!Population Size!

Births(come in)Births(come in) Deaths(go out)Deaths(go out) Immigration(move in)Immigration(move in) Emigration(move out)Emigration(move out) (Age structure is important in (Age structure is important in

determining if a population is likely to determining if a population is likely to grow or decrease. )grow or decrease. )

Biotic PotentialBiotic Potential

Biotic potential is the Biotic potential is the capacity for populations capacity for populations to grow under ideal to grow under ideal conditions.conditions.

Huge animals like Huge animals like elephants and whales elephants and whales have low biotic potential.have low biotic potential.

Bacteria and insects Bacteria and insects have high biotic potential have high biotic potential

The INTRINSIC RATE OF INCREASE (r) is the rate The INTRINSIC RATE OF INCREASE (r) is the rate at which the population of a species would grow if at which the population of a species would grow if it had unlimited resources.it had unlimited resources.

Populations with high (r) have individuals that Populations with high (r) have individuals that reproduce early, have short generation times, reproduce early, have short generation times, reproduce many times, and have many offspring reproduce many times, and have many offspring each time they reproduce.(Example:Bacteria) each time they reproduce.(Example:Bacteria)

No population can grow indefinitely because of No population can grow indefinitely because of limiting factors such as light, water, space, and limiting factors such as light, water, space, and food, or exposure to competitors, predators, or food, or exposure to competitors, predators, or disease. THERE ARE ALWAYS LIMITS TO disease. THERE ARE ALWAYS LIMITS TO POPULATION GROWTH)POPULATION GROWTH)

Environmental Resistance is the combination of all Environmental Resistance is the combination of all factors that act to limit population growth. factors that act to limit population growth.

Together, biotic potential and environmental Together, biotic potential and environmental resistance determine CARRYING CAPACITY (K): resistance determine CARRYING CAPACITY (K): the maximum population of a given species that a the maximum population of a given species that a particular habitat can sustain indefinitely without particular habitat can sustain indefinitely without being degraded. being degraded.

The growth rate of a population decreases as its The growth rate of a population decreases as its size nears the carrying capacity of its environment. size nears the carrying capacity of its environment.

Food and Space are getting Food and Space are getting scarce scarce Carrying capacity Carrying capacity reached. Fewer fishes. reached. Fewer fishes.

EXPONENTIAL GROWTH: starts slowly, EXPONENTIAL GROWTH: starts slowly, accelerates quickly. (Few limitations on accelerates quickly. (Few limitations on growth. Many resources.) This is shown on growth. Many resources.) This is shown on graph as a J-shaped curve. graph as a J-shaped curve.

LOGISTIC GROWTH: involves rapid LOGISTIC GROWTH: involves rapid exponential growth followed by a steady exponential growth followed by a steady decrease until population levels off. decrease until population levels off. (Dwindling resources) This is shown as an (Dwindling resources) This is shown as an S-shaped curve on a graph. S-shaped curve on a graph.

Changes in the population of a keystone Changes in the population of a keystone species such as the southern sea otter or species such as the southern sea otter or the American alligator can alter the species the American alligator can alter the species composition of an ecosystem. composition of an ecosystem.

Example: Decline in sea otters caused a Example: Decline in sea otters caused a decline in species dependent on them, such decline in species dependent on them, such as giant kelp. This reduced species as giant kelp. This reduced species diversity in kelp forests and altered its diversity in kelp forests and altered its functional biodiversity by upsetting food functional biodiversity by upsetting food webs and reducing energy flows and webs and reducing energy flows and nutrient cycles. nutrient cycles.

I am endangered. I am endangered. Read Read about my plight on p. 110about my plight on p. 110

I EAT SEA OTTERS!! I EAT SEA OTTERS!!

Parasites in my tummy Parasites in my tummy make sea otters sick!! make sea otters sick!!

Moving on…..Moving on…..

Sometimes a population Sometimes a population grows so fast that it doesn’t grows so fast that it doesn’t transition from exponential transition from exponential to logistic growth to logistic growth smoothly….alas, it smoothly….alas, it temporarily OVERSHOOTS, temporarily OVERSHOOTS, or exceeds the carrying or exceeds the carrying capacity of the capacity of the environment. (Caused by environment. (Caused by reproductive time lag) reproductive time lag)

Then the population suffers Then the population suffers a DIEBACK, or CRASH, a DIEBACK, or CRASH, unless the excess unless the excess individuals move to new individuals move to new resources or switch to new resources or switch to new resources. resources.

REPRODUCTIVE REPRODUCTIVE PATTERNSPATTERNS

R-SELECTED SPECIES: species with a R-SELECTED SPECIES: species with a capacity for a high rate of population capacity for a high rate of population increase (r). increase (r).

Have many small offspring. Little parental Have many small offspring. Little parental care. care.

Big numbers of babies offset large losses. Big numbers of babies offset large losses. Reproduce and disperse rapidly when Reproduce and disperse rapidly when conditions are right. conditions are right.

Opportunistic. Opportunistic.

We take advantage!!We take advantage!!

K-SELECTED SPECIESK-SELECTED SPECIES: : These are These are competitor species. competitor species.

Reproduce later in life. Have fewer Reproduce later in life. Have fewer offspring. Born larger. Cared for by parent. offspring. Born larger. Cared for by parent.

More competitive for resources. More competitive for resources. Follow logistic growth curve. Follow logistic growth curve. Can be prone to extinction, especially if Can be prone to extinction, especially if

heavily hunted. heavily hunted.

We are “K-Select”We are “K-Select”

r-select K-selectr-select K-select on the farm!! on the farm!!

Genetic Diversity in Small Genetic Diversity in Small Populations! It can be Populations! It can be lost!lost!

Founder Effect: a few Founder Effect: a few individuals in a individuals in a population colonize a population colonize a new habitat that is new habitat that is geographically geographically isolated from the rest isolated from the rest of the population. of the population.

These foxes live in These foxes live in isolated areas. isolated areas.

Demographic Demographic bottleneckbottleneck: : Only a few Only a few individuals survive a individuals survive a catastrophe. Lack of catastrophe. Lack of genetic diversity may genetic diversity may limit their ability to limit their ability to rebuild population. rebuild population.

Even if population Even if population increases, lack of increases, lack of genetic diversity may genetic diversity may lead to an increase of lead to an increase of genetic diseases. genetic diseases.

Genetic Drift: Random Genetic Drift: Random changes in gene frequency changes in gene frequency may lead to unequal may lead to unequal reproductive success. reproductive success.

Some individuals may Some individuals may breed more, so their genes breed more, so their genes dominate. This could help dominate. This could help or hinder the population’s or hinder the population’s survival. survival.

This is similar to founder This is similar to founder effect or bottleneck. effect or bottleneck.

Example: polydactyly in Old Example: polydactyly in Old Order Amish. Order Amish.

InbreedingInbreeding: : Occurs when individuals Occurs when individuals in a small population mate with one in a small population mate with one another. another.

Can occur through bottleneck.Can occur through bottleneck. Increases frequency of defective Increases frequency of defective

genes. genes. Example: Hapsburg royal familyExample: Hapsburg royal family

POPULATION DENSITYPOPULATION DENSITY

Population Density: the number of individuals in a Population Density: the number of individuals in a population found in a certain area. population found in a certain area.

Density-dependent population controls include Density-dependent population controls include predation, parasitism, infectious disease, and predation, parasitism, infectious disease, and competition. These have a greater effect as competition. These have a greater effect as population density increases. population density increases.

Density-independent population controls are not Density-independent population controls are not dependent on population density: severe freeze, dependent on population density: severe freeze, floods, hurricanes, fire, pollution, habitat floods, hurricanes, fire, pollution, habitat destruction. destruction.

4 Patterns of Variation in 4 Patterns of Variation in Population SizePopulation Size

STABLE: fluctuates STABLE: fluctuates only slightly above only slightly above or below carrying or below carrying capacity. capacity.

Example: tropical Example: tropical rainforest speciesrainforest species

IRRUPTIVE: IRRUPTIVE: explodes with a explodes with a high peak, then high peak, then crash! Gets stable crash! Gets stable or goes low. or goes low.

Example: Example: Temperate climate Temperate climate insectsinsects

CYCLIC: cyclic CYCLIC: cyclic fluctuations or boom fluctuations or boom and bust cycles. and bust cycles.

Examples: lemmings, Examples: lemmings, lynx and hare.lynx and hare.

Top-down regulation is Top-down regulation is through predation.through predation.

Bottom-up regulation Bottom-up regulation is by scarcity of is by scarcity of resources. resources.

IRREGULAR: No IRREGULAR: No recurring pattern. recurring pattern. Chaos, catastrophe, Chaos, catastrophe, severe weather.severe weather.

Examples: Bubonic Examples: Bubonic plague, potato plague, potato famine, AIDSfamine, AIDS

YAY!! TECHNOLOGY!!YAY!! TECHNOLOGY!!

Technological, Technological, social, and other social, and other cultural changes cultural changes have extended the have extended the earth’s carrying earth’s carrying capacity for the capacity for the human species. human species.

Read about the White-Read about the White-Tailed Deer. pp.114-15Tailed Deer. pp.114-15