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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
 Speciation
 Extinction
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
A group of bacteria,
including genetically
resistant ones, are
exposed to an
antibiotic
Normal
bacterium
Resistant
bacterium
Most of the normal
bacteria die
The genetically
resistant bacteria
start multiplying
Eventually the
resistant strain
replaces the strain
affected by
the antibiotic
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
environments
 Small body size
 High fecundity
 Early maturity
 Short generation time
 Less parental care
K selected
 Stable
environments
 Large body size
 Long life expectancy
 Later maturation
 Few offspring
 More parental care
Reproductive Strategies
R- 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 Curves
Type
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.
Speciation
One species splits into two of more different species
Two mechanisms:
1. Geographic Isolation
2. Reproductive Isolation
Geographic Isolation
Occurs when a population become
physically isolated from one another for a
long period of time
mountains
rivers
landslides
Reproductive Isolation
Differences in isolated groups become
so great, they can no longer interbreed
– Behavioral changes
– Physical changes
– Genetic changes
Speciation in Action
California Salamanders
Extinction
Two Types
1. 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 Species
Species 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 Species
So 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 Species
Sea Otters
Keystone Species
Grey Wolves
Invasive Species

A non native (introduced) species that
adversely affects a habitat they invade
ecologically and/or economically
Invasive Species
Where 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 Species
Species 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 species
2. 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
Which do you think is
more diverse?
A
B
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