Unit 14 Evidences
of Evolution CONCISE Notes
Study Link: https://quizlet.com/_1eakvz
1.
Natural Selection (lose
traits)
a. Acts on populations, not
individual organisms
b. Does not directly act on genes, only
how frequent a gene is found in a population
c. Describes
how organisms that are best adapted to their environment survive and
reproduce.
d. Causes
populations to change as certain organisms reproduce and pass on their genes to
future generations.
e.
f.
Ex. White, brown, and
black genes for rabbits exist; brown fur is more camouflaged and more likely to
survive and pass the trait to offspring; the white and black gene may disappear
2. Three Ways to Distribute Genes from
Natural Selection
a. Stabilizing Selection - favors the
“norm”
b. Directional Selection - favors one
extreme or the other
c. Disruptive Selection - favors both
extremes
3. Mutations and Adaptations
a. Random mutations change genetic code and are
responsible for creating the variety of
life
i.
Mutations
(gain traits) may be beneficial, harmful, or neutral – add genetic variation
1. May allow an organism to adapt in a
changing environment
b. Adaptations
are any traits, physical or behavioral, that help an organism survive
i.
Ex.
Forest rabbits may develop a mutation that causes albinism (white fur, pink
eyes); if the climate in the area changes so that snow covers the ground most
of the year, this mutation would be beneficial and be passed to other
generations; otherwise it is harmful
4.
a. Diversity is the variety of traits in
a species
b. Gene pool is the total number
of genes available to a species
c. Diversity allows species to adapt to
different environments
i.
Overcome
disasters (drought, famine, diseases)
d. Species that has
i.
Large
Gene Pool = Greater diversity = Better able to adapt and survive
ii.
Small
Gene Pool = Less diversity = Lower chance of survival
5.
Genetic Drift – (lose traits) the
change in the gene pool generated by chance – more likely in a small population
– immigration and emigration
a. By chance more brown-eyed insects are
born, and over time, the population drifts toward having brown eyes instead of
white
6. Threat of Extinction (lose traits) - few organisms
are available for mating and the species may die off, diversity has been diminished,
limited genes available to offspring
a. Example: The insects of the above
population are eaten by a predator. There are only a few insects of this
species left. If they do not reproduce, this species will cease to exist.
7.
The Founder Effect - a new colony formed by a small population with a limited
gene pool
a. Example: If only white eyed insects
survive, then there will be no brown eye gene to pass on. This may or may not
affect the survival of the population of insects. If there are any genetic
defects in these founding insects, they will most likely be passed on and occur
more often in the offspring.
8. Selective Breeding (artificial selection) (usually lose
traits, usually decrease diversity) – decreases gene pool as undesirable
traits are bred out – more susceptible to disease, pest, climate change
a. Farmers choose the crops that they
plant based on what is good to eat, beauty, and what grows well in their
climate. By doing this, the gene pool of the plants is reduced.
b.
Example: Wheat has
been harvested for thousands of years. Wheat grew wild in many kinds of
climates and it had a large gene pool. Farmers have remove undesirable traits
from wheat by cross-pollinating the plants and have created hybrids that grow
well in the current climate. If earth's climate were to change, wheat may not
be grown because its gene pool has been reduced by selective breeding.
c. However, sometimes breeders introduce
mutations into the gene pool causing a greater genetic variation. See the many
breed of dogs.
9. Mutations (gain traits) - changes in
the DNA that can ADD genetic variation
a. Example: In a population of moths,
dark wings are best adapted as its camouflages the moths with the dark bark of
the trees. Moths born with white wings due to a mutation in their DNA would
most likely be eaten by predators. However, if the climate changes and the bark
of the trees changes to a lighter color, then white wings would provide better
camouflage from predators.
10. Antibiotic, Pesticide, and Herbicide
Resistance - In order to keep people
healthy and well-fed, humans use chemicals to kill undesirable organisms – the
use of these chemicals leads to high rates of mutations and resistance
a. Bacteria have a high rate of
mutations and reproduce very quickly. They can become resistant to the
antibiotics we use in only a few generations.
In this way, natural selection allows these organisms to thrive.
11. Speciation - The formation of a new species
a. Occurs when members of a population
no longer interbreed
b. Caused by Isolation:
i.
Geographic Isolation
1. A physical
barrier that divides a population into two or more separate groups; lack of
interbreeding leads to adaptations
a. volcanic
eruption, separation of land into islands
2. Smaller populations may adapt in
different ways, become new species
ii.
Temporal Isolation
1. a species
develops different reproductive cycles
a. pollination or reproduction occurs at
different times; day or night, spring or fall
2. Become so different that they can no
longer interbreed
iii.
Behavioral Isolation
1. When two
populations do not interbreed because of differences in courtship behaviors.
a. Ex – bird
songs, dances, mating calls
12. Evidence for
Evolution
a. Adaptations
i.
Structural
adaptations - Change in an organisms body parts
1. Mimicry - allows one species to resemble another
a. king snake
resembles coral snake
2. Camouflage - allows a species to blend into their
surroundings
ii.
Physiological
adaptations - changes in an organisms metabolic processes – happen quickly
1.
Weeds are become resistant to
pesticides, bacteria become resistant to antibiotics
b. Fossils - Used to form timelines from one species to another
that evolved from it
1. Fossil - remains of organisms covered
in mud or clay shortly after death
2. Most are found in sedimentary rock
3. Petrify
–(fossilize) minerals replace wood,
shells, bone
ii.
Age
of Fossils
1. Relative Dating - Lowest layer of
sedimentary rock oldest fossils
2. Radiometric Dating – measure the
amount or radioactive isotopes in the fossil
3.
Half-life – the time
it takes for a radioactive material to decay into a different material; Carbon
dating – tell how old it is
c. Comparative anatomy
i.
Compare
modern species with species believed to exist millions of years ago
1. Determine what changes occurred and
why
ii.
Homologous structures - Structural features with a common evolutionary
origin.
1. Develop from the same tissues as embryos and have
similar internal structures. They may
look different on the outside, and they may have different functions
2. Ex. The forelimb of a human, a bat, a crocodile, and a
bird have similar skeletal structures, but have different functions
3. Evidence that organisms evolved from a common
ancestor.
a. Whale fin, Crocodile limb, bird wing, human arm
iii.
Vestigial
structures - body structures that has
no present day use, but was useful to an ancestor
1. A structure that seems to have no useful purpose now
although they resemble structures that are useful in other species
2. Ex. Ostrich have wings that don’t work, cave
salamander have eyes that don’t work, pelvis bond in some whales
3. Ostrich forelimbs, Human appendix
iv.
Analogous
Structures – NOT EVIDENCE
1. Structures
that have similar functions but are not believed to have evolved from a
common ancestor
a.
Ex. A birds wing and
a butterfly wing have similar function but are structurally different
d. Embryology - Comparing Embryos of different species for
similarities
i.
Embryos,
earliest stage of development, of different species look similar, may have a
common ancestor
e. Biochemistry – comparing DNA and RNA of different species
i.
Humans and
gorillas share 98% of the same DNA
ii.
Humans and
bananas share 70% of the same DNA
13. Punctuated Equilibrium
a.
idea that suggests that long intervals in which little or no change
occurs are suddenly interrupted by short bursts of quick, radical transitions –
explains gaps in fossil record
14. Gradual
Evolution (Gradualism)
a. new species evolve from existing
species through gradual, often imperceptible changes rather than through
abrupt, major changes
15. Most scientists believe a combination
of gradual evolution and punctuated equilibrium occurred over time
16. Biogeography
a.
The study of how plants and animals are distributed around the world
b. Depends on
the migration ability of a particular species and how plants and animals have
been separated from one another over time by continental drift (the movement of
the continents)
i.
Plate
Tectonics
1. the
surface of the earth is divided into large plates that continually move
2.
Pangaea – all landmasses were once connected in a single continent
c. Ex. Apes are found only in
Africa and Asia; these species must have been separated from a common ancestor
early in their history and then evolved differently
17. Divergent Evolution
a. New
species “diverge” or split from a common ancestor
b. Ex. Apes
and humans diverged from a common ancestor
c.
Adaptive Radiation
i.
Kind
of divergent evolution in which one ancestral species splits into many
related species
18. Convergent Evolution
a. Organisms
that have similar characteristics but are not considered closely related
i.
Like sharks (fish) and dolphin (mammal)
19. Coevolution
a.
A pattern of evolution in which two species must have evolved, or
changed, together.
b. Ex-
flowering plants and the insects that pollinate them are believed to be
examples of coevolution
20. Cladogram
and Phylogenic Tree – a diagram that shows the relationship between species
a. The
organisms have a common ancestor
b. The bottom
of the cladogram is the furthest in the past
c. Organisms that
come from the same branch are closely related, like the kangaroo and koala
d.
Kangaroos, koalas,
bats, and lions are have a common ancestor; they are all mammals
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