Biodiversity

Biodiversity

The variety of Earth’s species, the genes they contain, the ecosystems in which they live, & their functions in energy flow & nutrient cycling

Destroying the rain forest for economic gain is like burning a Renaissance painting to cook a meal.

~ E. O. Wilson

Three Components

What affects biodiversity?

Natural Selection/Evolution

SpeciationExtinction

Evolution

Change in a species’ genetic makeup over time

Natural Selection

Individuals with certain traits are more likely to survive and reproduce under a particular set of environmental conditions than those without the traits

Begins with mutations

Adaptation Video

Resistance

Most of the normal bacteria die

The genetically resistant bacteriastart multiplying

Eventually the resistant strainreplaces the strain affected bythe antibiotic

A group of bacteria, including genetically resistant ones, areexposed to an antibiotic

Normal bacterium

Resistant bacterium

Limits to Natural Selection

When a change in environmental conditions occurs, a gene/mutation must already occur in the population

Reproductive capacity– Fast reproduction = quicker adaptation– Slow reproduction = slow adaptation

r Selected Unstable

environmentsSmall body sizeHigh fecundityEarly maturityShort generation

timeLess parental care

K selected Stable environmentsLarge body sizeLong life expectancyLater maturation Few offspringMore parental care

Reproductive StrategiesR- strategists K-strategists

Mature rapidly Mature slowly

Short lived Long lived

Tend to be prey Tend to be both predator and prey

Have many offspring and overproduce Have few offspring

Low parental care High parental care

Generally not endangered Most endangered species are K-strategists

Wide fluctuation in population density (booms and busts)

Population stabilizes near carrying capacity

Population size limited by density-independent factors (climate, weather, natural disasters, requirements for growth)

Density-dependent limiting factors to population growth stem from intraspecific competition and include predation, parasitism, and migration

Tend to be small Then to be larger

Type III survivorship curve Type I or II survivorship curve

Examples: most insects, annual plants, bacteria, rodents

Examples: humans, elephants, cacti and sharks

Survivorship Curves

Show age distribution characteristics of species, reproductive strategies and life history.

Reproductive success means how many organisms make it to maturity and reproduce

Survivorship CurvesType Descriptions

I Late Loss Reproduction occurs fairly early in life. Most deaths occur at the limit of biological life span. Low mortality art birth. High probability of surviving to advanced age. Advances in prenatal care, nutrition, disease prevention and cures mean longer life spans for humans. Examples: humans, annual plants, sheep and elephants.

II Constant Loss

Individuals in all age categories have fairly uniform death rates. Predations affecting all age categories is primary means of death. Typical of organisms that reach adult stages quickly. Examples: rodents, perennial plants and songbirds.

III Early Loss Typical of species that have great numbers of offspring and reproduce for most of their lifetime. Death is prevalent for younger members of the species (environmental loss and predation) and declines with age. Examples: sea turtles, trees, internal parasites, fish and oysters.

SpeciationOne species splits into two of more

different species

Two mechanisms:1. Geographic Isolation2. Reproductive Isolation

Geographic Isolation

Occurs when a population become physically isolated from one another for a long period of time

mountains riverslandslides

Reproductive Isolation

Differences in isolated groups become so great, they can no longer interbreed

– Behavioral changes– Physical changes– Genetic changes

Speciation in ActionCalifornia Salamanders

Extinction

Two Types1. Biological

– The process in which an entire species ceases to exist

Local– A population of a species becomes

extinct over a large region but not globally

Passenger Pigeon 3-5 billion – first European settlers Last died 1914

– Cincinnati zoo - Martha Caused by

– Habitat destruction – Over hunting

Endemic SpeciesSpecies only found in one area

•Highly vulnerable to extinction

Types of Biological Extinction

Background extinction– Species disappearing at a slow rate

Mass extinction– Significantly high rate of extinction– 25-95% of global species gone

• Largest Permian – 96% of species died

– Promotes evolution

Endangered SpeciesSo few individuals that the species could become

extinct

– Reasons• Habitat loss/fragmentation• Loss of keystone species• Invasive species• Climate change• Pollution • Overcosumption

Keystone Species A species that plays a critical role in

ecosystem structure & whose impact on the community is greater than expected based on abundance

Removal greatly affects the food web

Keystone SpeciesSea Otters

Keystone SpeciesGrey Wolves

Invasive Species A non native (introduced) species

that adversely affects a habitat they invade ecologically and/or economically

Invasive SpeciesWhere do they come from?• Horticulture• Conservation• Accidental

Invasive Species Characteristics

Tolerate a variety of habitat conditions

Reproduce rapidly– Short generation time

Great competitors– generalist

Lack of predators Genetic variability

Indicator SpeciesSpecies that provide early warning signs of damage to

an ecosystem

Examples:Lichens (air quality)Stoneflies (aquatic – DO)Pika – (climate change)

Levels of Diversity

Ecosystem Diversity– Different habitats,

niches, interactions Species Diversity

– Different types of organisms

Genetic Diversity – Different genes &

combinations within a population

Measuring Species Diversity

Two components:1. Species richness

• Number of unique species2. Species evenness

• Number of individuals of each species in an area

Monoculture Opposite of biodiversity Growing only one species of

organism Problem?

– disease

Which do you think is more diverse?

A B

Which do you think is more diverse?

A B

A B

Which do you think is more diverse?