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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?
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