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Biodiversity and Evolution
Chapter 4
What is Biodiversity?
• The variety of Earth’s species, the genes they
contain, the ecosystems in which they live,
and the ecosystem processes such as energy
flow and nutrient cycling that sustain all life.
• Species
– A group of organisms with a set of characteristics
that distinguish it from other groups of organisms.
– Must be able to reproduce fertile offspring with
other members within the species.
• Species diversity vs.
genetic diversity.
• Ecosystem diversity
– Biomes: large regions
such as forests, deserts,
and grasslands with
distinct climates and
certain species.
Earth’s Change Over Time
• Biological Evolution by Natural Selection
explains how life changes over time.
– Individuals with certain traits are more likely to
survive and reproduce under a particular set of
environmental conditions than those without the
traits.
– Populations evolve. Not individuals.
Charles Darwin
• Theory of Evolution by natural selection:
– Individuals produce more offspring than survive.
– Individuals differ in their traits
– Traits can be passed on from parents to offspring.
– Some traits are more favorable than others (allow an
organism to survive and reproduce)
• Fitness: an ability to survive and reproduce
• Adaptations are traits that improve an individual’s fitness.
What’s necessary for evolution to
occur?
• Genetic Variability
– Mutations
– Recombination
• Genes – segments of DNA that code for possible
traits that can be passed down to offspring.
– A complete set of genes is called genotype.
Genotype vs. Phenotype
• Phenotype can be influenced by just genotype
or a combination of genotype and environment.
Evolution by Artificial Selection
• When humans determine which individuals breed.
• Artificial Selection has produced numerous breeds of dogs,
horses, cattle, sheep, pigs, and chickens with traits humans find
useful or aesthetically pleasing.
Evolution by Random Process
• Mutations
Evolution by Random Process
Genetic Drift
Evolution by Random Processes
The Bottleneck Effect
Evolution by Random Process
Founder Effect
Allopatric Vs. Sympatric Speciation
• Allopatric Speciation:
– Geographic Isolation – physical separation of
members of a population resulting in different
genotypes between the two new populations.
– Reproductive Isolation – Genotypes of two
populations become so different, they can no longer
reproduce with one another.
Allopatric Vs. Sympatric Speciation
• Sympatric Speciation:
– Polyploidy – number of chromosomes increase. Once an
organism becomes polyploidy, they cannot reproduce
with their diploid ancestors.
• Often results either intentionally or non-intentionally in
salamanders, snails, agricultural crops, etc.
• Results in larger fruits and larger plants.
Rate of Evolution
• The ability of a species to survive an environmental
change depends greatly on how quickly it evolved the
adaptations necessary to thrive and reproduce.
– Rate of Environmental Change
– Genetic Variation
– Population Size
– Generation time