Download Ch. 15

Ch. 15 The Theory of Evolution
15.1 Natural Selection and the Evidence for Evolution
A. Charles Darwin and Natural Selection – evolution is the ______________________________
____________________________________ Charles Darwin (1809-1882) helped develop this theory.
1. ______________ shape ideas about evolution – paleontologists study fossils to learn about
extinct organisms and determine any _______________________ with living species.
2. Darwin on HMS Beagle – at age 21, he took a job as a Naturalist on a boat that went to
South America and the ______________ Islands.
3. ______________ in the Galapagos - While there, he noticed that animals on the mainland
looked and behaved differently than animals on the island. This led him to develop his theory of
evolution based on natural selection.
4. Darwin’ natural selection – ________ concepts explaining a mechanism for change in populations
1. In any population, _________
______________ are produced
than can survive. Ex: white
moths outnumbered dark moths
before the industrial revolution
2. ______________ exist
within any population.
Ex: light moths blended
into tree bark
3. Some of these
variations are _________
Ex: Soot turned tree bark
black and dark moths
blended in better
4. Those with favorable
variations are better able to
______________ and
____________________. Ex:
After, dark outnumbered white
B. Adaptations for Evolution – _______________________________________________________
_____________________________________ which make an organism more suitable for survival
1. Structural adaptations arise over time – for a ____________ in the genetic code to cause a
change in the population, the organism must be able to ______________ and _______________. Most
mutation are harmful and cause death. For example, Some scientists believe that mole rats have lost
their genetic ability for sight or even some animals have randomly mutated to mimic other organisms.
a). ________________________ – a structural adaptation that enables one species to
resemble another
b). _____________________– an adaptation that enables a species to blend into its
environment
2. Physiological adaptations can develop rapidly – some antibiotics are not as effective as they
once were. Ex: penicillin does not have the effect that it used to
C. Other evidences for Evolution –
1. ________________ – Paleontologist look to
the fossil record to find transitional forms of organisms.
They do not have intermediate forms for most species.
The fossil record is incomplete
2. ________________ – similar anatomical
structures are thought of as evidence of evolution from a
common ancestor. Ex: forelimbs of vertebrates
a). ________________ ________________
– structures similar in arrangement, function, or both
b). ________________ ________________ – share a similar function but no common
ancestor
c). ________________ ________________ –
structure that may have once function but currently does
not. Ex: flightless birds,
3. __________________________– similarities
between early stages of life
4. ________________________– DNA evidence shows that living organisms use nucleic acid
to hold genetic information. DNA sequences can show how closely organisms are related.
15.2 Mechanisms for Evolution
A. Population Genetics and Evolution– the gene pool determines the traits of a population
1. Populations, not individuals, evolve – characteristics acquired in an individuals life are not
passed on to their offspring. ___________________________________________________________
can bring change to future generations
a). ________________ ________________ – all the alleles of a populations genes
b). ________________ ________________ – the percentage of any specific allele in the
gene pool
c). ________________ ________________ – a population in which the frequency of alleles
remains the same over generations
2. Changes in genetic equilibrium – a population that is in genetic equilibrium in not evolving.
There are 4 major causes for change in a population.
a.
Most mutations result in
death or a disorder but
some scientists think they
could help an organism
survive and reproduce
b.
The alteration of allelic
frequencies by chance
events. Changes in small,
isolated gene pools
Ex: 6 fingered Amish
c.
Immigration and
emigration
bringing new
genes to
population
d.
Survival of the
fittest
3. Natural Selection acts on _________________________ – there are three different types of
natural selection that act on variation: stabilizing (most common), directional and disruptive.
a).
natural selection that favors
average individuals in a
population
Ex: human birth weight: too
small and can’t survive on its
own, too large and can’t fit
through the birth canal
b).
natural selection that favors
one extreme variation for a
trait
Ex: selection of dark peppered
moths after the industrial
revolution turned the lichen on
trees dark
c).
Natural selection that favors
individuals on either extreme of a
trait’s variaiton
Ex: mostly theoretical examples
exist. Possibly Darwin’s finches
who populated the islands vs. the
mainland
B. The Evolution of Species – evolution is the change in a species over time. Mutation, genetic
drift, gene flow and natural selection can change a gene pool over time. These are examples of
_____________________________. ________________________________ would be the theory of
all life evolving from a single celled organism over long periods of time to all the kingdoms of life
(Bacteria, Protist, Fungi, Plant, and Animal). The evolution of a new species is called speciation
a). _______________________- occurs when members of similar populations no longer
interbreed to produce fertile offspring within their natural environment.
1. Physical barriers can prevent interbreeding – water, mountains, volcanoes, storms…
a). _______________________ _______________________ – occurs whenever a physical
barrier divides a population
2. Reproductive isolation can result in speciation – as a population becomes increasingly
distinct, reproductive isolation can arise
a). ________________ ________________ – occurs when formerly interbreeding
organisms can no longer mate and produce fertile offspring
Ex: wood frogs usually breed in late March/early April while leopard frogs usually breed in mid-April
3. A change in chromosome numbers and speciation – ________________________________
_____________________ can result in polyploid individuals
a). ___________________ – any species with a multiple of the normal set of chromosomes.
Ex: many flowering plants, wheat, cotton, apples, bananas
4. Speciation can occur quickly or slowly – Scientists once argued that evolution occurs at a
slow rate and that adaptive changes gradually accumulated over time in populations.
a). ________________ – is the idea that species originate through a gradual change of
adaptations
Ex: camel fossils
b). ________________ ________________ – this hypothesis argues that speciation occurs
relatively quickly, in rapid bursts (10,000 years) with long periods of genetic equilibrium in between
Ex: elephant fossils
C. Patterns of Evolution – natural selection is an important agent for change
1. Diversity in new environments – geographically isolated places (ex: Galapagos islands)
decreases the size of the gene pool and can lead to the microevolution of a species. Ex: Hawaiian
honey creepers. Adaptive radiation is a type of divergent evolution that usually stems from a change in
the environmental conditions (storms, fire, flood, natural disaster…)
a). ________________ ________________ – when an ancestral species evolves into an
array of species to fit a number of diverse habitats
b). ________________ ________________ – the pattern of evolution in which species that
once were similar to an ancestral species diverge, or become increasingly distinct.
2. Different species can look alike – occurs when unrelated species occupy similar
environments in different parts of the world and share similar pressures of natural selection
a). ________________ ________________ – a pattern of evolution in which distantly
related organisms evolve similar traits
Ex: Euphorbia tree (Africa) and the organ pipe cactus (N. and S. America)