BIOLOGY 1M03 Lecture Notes - Lecture 25: Aniridia, Ectopic Expression, Sebaceous Cyst
29 Jun 2018
School
Department
Course
Professor
Chapter 24 – Evolution by Natural Selection
Key Concepts
Evidence of evolution (change through time, extinction, vestigial traits, inter-relatedness).
Evidence of natural selection (industrial melanism, antibiotic resistance, beak size in
Galapagos finches)
Natural selection affects individuals by influencing reproduction, but evolution occurs in
populations over time*. Epigenetics where we see that methylation can have a significant
impact on genes and can later gene expression and can be passed on to the next
generation. While either Darwin or Wallace be thinking of reproductive success/ genetic
variation as the main contributor to adaptation. There are a few findings that relate to
epigenetics and environment that influences the chemical state of DNA that suggests
that experience changing phenotypic changes in offspring. But we focus on gene
frequencies due to reproduction success in generations
The Evolution of Evolutionary Thought
Darwin and Wallace went a major step farther and proposed that change in species over
time is based on natural selection acting on heritable variation among individuals.
The Evolution of Evolutionary Thought
Darwin described evolution as descent with modification, meaning that change over time
produced modern species from ancestral species.
A lot of evidence is seen for evolution. One of the examples: physical characteristics or
phenotypes change over time. This is seen when you compare different species that are
around today and also when you compare using fossil records. This photo here shows
the bone structure of Lob-finned fish, you can see that the bone structures (even though
they aquatic creatures) are is similar to tetrapod’s and early amphibian.
This means that species: (1) change through time, and (2) are related by common
ancestry
Is there really much evidence for evolution?
Fossils – we can observe fossils of species that were around previously that we don’t
have evidence of today. This trilobite is half a million year old according to fossil record.
They have gone extinct, they don’t occur today, so clearly there have been differences in
one species to another to come where about today.
We also see evidence of humans leaving footprints very long ago. These are hominid
footprints, which are 3.6 million years ago. Ancestors of modern day humans, they left
tracks in dirt.
Evidence for Change through Time: Extinction
Many fossil provide evidence off extinct species, those that are no long living
Evidence for Change through time: Prehistoric turds and ancient DNA
For example, sloths used to exist, in much more diversity than they are today and they
used to be giant sloths that would walk around central America and south America. You
can actually extract the DNA of extinct species from doing DNA extraction from fossil
records. You can see the DNA from ancient sloths and compare it to modern sloths. You
will be able to see the DNA differences. So not only are there morphological differences
but there are also genetic differences, which define these species which no longer exist.
Also allows us to make inferences on relationships between species.
Evidence for Change through Time: Transitional Forms
As the fossil record has become more complete, many transitional forms have been
discovered with traits that are intermediate between earlier and later species.
For example, we think that hippos and whales share a common ancestor and that this
terrestrial organism could have eventually diverged in descendent species and laon the
way to becoming a whale, they became more and more aquatic and they became
find more resources at oneclass.com
find more resources at oneclass.com
whales. We can see there is fossil record for individuals – progressive loss of limbs
where first we see at ranstion into
Examples include limb development and loss, feathers and flight, upright posture and
brain size in humans, jaws in vertebrates
Evidence for Change through Time: Vestigial traits
Even in our bodies we have changes that have evolved from our ancestors
Vestigial trait – a characteristic of an organism that is generated by the ancestor and has
been changed from that form. Chagned through evoltuoin, egernatlly less
Goosebumps – when you get cold, it turns out that Goosebumps don’t generate heat,
shivering generates heat, don’t have a function in humans. We can look in our close
relatives in chimpanzees - having upright hair is used in communication, to communicate
aggression or fear. The idea that goosebumps are still in humans is time when humans
had more hair or ancestors had hair. Legacy of that ancestor
Tailbone in humans – so this a of our acnestory with monkeys which have tails. _____
Some whales – have vestigial
Species change over
Evidence for Change through Time : Speciation and Evolution
Artificial selection
Speciation of fruit flies by divergence of host plant usage (e.g. the apple maggot fly
Rhagoletis)
Evolution of herbicide, pesticide, and antibiotic resistance
Evidence that species are related: Geographic continuity
Early scientists observed that extinct fossil species are typically succeeded, in the same
region, by similar living species
Darwin and Wallace interpreted this as evidence that extinct forms and living forms are
related, that they represent ancestors and descendants
Mockingbird species in the Galapagos are more closely related to each other than any is
to a species from the mainland
Observation that the geographic distribution is nonrandom. If you were to make a bunch
of species and spread them in open space you wouldn’t expect to group -
Geographic distributions of Mammals also reflects ehtier phylogenetic history
On a finer geographic scale, relationships among species of macaque monkey on
Sulawesi also show strong geographic structure
Conclusion
Species once existed that do not exist now (species change over time)
Morphological evidence of transitions and vestigial traits (species change over time)
Species that live today seem to be similar to fossils from the same place (ancestors
evolve into descendants)
Closely related species tend to occur in close geographic proximity to one another
(ancestors evolve into descendants)
Last Time
Giraffe necks: food and fighting. The origin and evolution of giraffe neck and we had two
hypotheses which could both be right. One hypothesis is that it gave giraffe an
advantage because they can access food resources at height. Second hypotheses -
sexual selection and the idea was that males with long necks were better at fighting and
therefore were able to access females. Those are not mutually exclusively, both can
explain how long necks evolved, in other words long neck had greater fitness than other
individuals and that over many generations it led to long necks
Naked mole rats and feces. We talked about how we can test the hypothesis that they
use community latrine as a way to recognize individuals in their colony. The idea being
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
Evidence of evolution (change through time, extinction, vestigial traits, inter-relatedness). Evidence of natural selection (industrial melanism, antibiotic resistance, beak size in. Natural selection affects individuals by influencing reproduction, but evolution occurs in populations over time*. Epigenetics where we see that methylation can have a significant impact on genes and can later gene expression and can be passed on to the next generation. While either darwin or wallace be thinking of reproductive success/ genetic variation as the main contributor to adaptation. There are a few findings that relate to epigenetics and environment that influences the chemical state of dna that suggests that experience changing phenotypic changes in offspring. But we focus on gene frequencies due to reproduction success in generations. Darwin and wallace went a major step farther and proposed that change in species over time is based on natural selection acting on heritable variation among individuals.
