There are three main patterns of evolution: convergent evolution, divergent evolution, and coevolution. Convergent evolution occurs when unrelated species independently evolve similar traits due to adaptation to the same environment. Divergent evolution is when species with a common ancestor evolve differences in traits over time. Coevolution is when two species influence each other's evolution, such as through a predator-prey relationship. Genetic variation within populations is driven by mutation, recombination, gene flow, and genetic drift, and this variation provides the raw material for natural selection to act upon as populations adapt to their environments over generations.

1. Patterns of Evolution
◼ Convergent evolution
◼ Divergent evolution
◼ Coevolution

2. Convergent Evolution
◼ Species that have no common origin but look or
behave similarly due to adaptation to the same
environmental condition come under his group
◼ The best example of this is hummingbirds and
sunbirds. Both these birds are from different
family but their feeding habit is the same. Other
examples include silk spiders and silk moths,
bats and birds

3. CONVERGENT EVOLUTION
ocotillo (left) from the American Southwest, and in the allauidia (right)
from Madagascar

4. Divergent Evolution
◼ Divergent means landing at
different points. Species that
have a common origin but
have differences in
morphology or show
differences in their behavior
come under this group
◼ Examples include limbs with
five-digit of bat and whale;
that evolved from a common
ancestor but their use and
function are different

5. Co-evolution
◼ Refers to effect of two species on each
other’s evolution. This can be seen in
insects and plants where one act as
predator and other s prey thus affecting
the morphology of each other.

6. Bumblebees and the flowers the they pollinate
have co-evolved so that both have become
dependent on each other for survival.

7. COEVOLUTION
Praying Mantis simulates plant to protect itself
from predators and eats pests that are attracted to
and feed on the plant, so it protects the plant.

8. COEVOLUTION
Coevolution between the
yucca moth and the yucca
plant. (right) A female
yucca moth pushing pollen into the stigma
tube of the yucca flower
while visiting the flower
to deposit her eggs.
Yucca moth larvae (left)
feeding on seeds in
the yucca fruit.

9. Evolution
◼ Is defined as a change in the genetic
composition of a population over successive
generations.
◼ Evolutionary changes involve interaction
between available genetic variants and the
environment in which they exist. For
evolution to proceed, there are vital key
players: genetic variation, natural
selection, and genetic drift

10. Genetic Variation
◼ Heritable
◼ Transmittable traits are those encoded in
the genes
Sources of variation:
Mutation
❑ A change in the genomic DNA either by
random replication errors or by
environmental interaction with DNA
nucleotides

11. Genetic Variation
Sources of variation: Increase variation
Mutation
❑ Gene Flow - The introduction of new
mutations into a population by
individuals migrating from a different
population.

12. ◼ If genetic variants are carried to a
population where they previously did not
exist, gene flow can be an important source
of genetic variation
◼ A beetle carries the gene version for brown
coloration from one population to another.

13. ◼ Transfer of alleles or genes from one
population to another (of the same species)
by migration

14. Genetic Variation
Sources of variation:
Increase variation
Recombination
❑ Is usually a consequence of
sexual reproduction in
eukaryotes.
❑ Crossing over - during meiosis,
sections of homologous
chromosomes align and swap
segments of genes
❑ Meiosis results in the
production of gametes that are
genetically different from each
other and the parent

15. Sources of Variation: decrease variation
Genetic Drift
❑ Random change (due to "sampling
error" in selecting the alleles for the next
generation from the gene pool of the
current generation) in the variation or
allele frequency of a population

16. we have a very small rabbit
population that's made up of
brown individuals (genotype
BB or Bb) and white
individuals (genotype bb).
Initially, the frequencies of the
B and b alleles are equal.
https://www.khanacademy.org/science/ap-
biology/natural-selection/population-
genetics/a/genetic-drift-founder-bottleneck

17. Bottleneck effect
◼ Event drastically reduces population size
◼ Survivors are not necessarily “fittest” but
live by chance and pass on genes
◼ Bottleneck event: natural disaster, disease,
habitat destruction

18. Founder effect
◼ Few individuals leave original population
and begin a new population
◼ New population contains only alleles
carried in by the founders

19. Non-random mating
◼ Some individuals are more likely to find a
successful mating partner, therefore more of
their alleles will be present in subsequent
generations
◼ Proximity: easier to mate with nearby
organisms
◼ Competition: fitter organisms are more
likely to out-compete other possible mating
partners and pass on their traits

20. Sources of Variation: decrease variation
Natural Selection
❑ Survival of the fittest leads to the
accumulation of favorable traits
❑ Fewer non-adaptive alleles remain in the
population