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[LIFESCI 15] - Midterm Exam Guide - Ultimate 13 pages long Study Guide!


Department
Life Sciences
Course Code
LIFESCI 15
Professor
Jay Phelan
Study Guide
Midterm

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UCLA
LIFESCI 15
MIDTERM EXAM
STUDY GUIDE

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Week 1 Lecture 3- Evolution
I. Evolution of Starvation Resistance
Sample experiment/question: How long can a fly survive without food? Can we
increase the average time of starvation in a population?
Every generation, let population die until you have last 20% left, then have then breed
and repeat
After 60 generations, flies could last for 160 hours without food
Flies started to be born differently (greasy and with less eggs) to prepare for
starvation
Take away message: species are not immutable; we can watch them change in nature
or even cause them to change
II. What is Evolution?
The gradual process in which something changes into a different and more complex
or better form
A change in allele frequencies within a population
Gene- a section of DNA instructing the body how to produce a trait through the
creation of proteins
Allele- one variant or version of a gene (we get one from each parent)
Individual can be homozygous dominant (BB), homozygous recessive (bb), or
heterozygous (Bb)
Allele frequency in a population can be measured by counting the number of each
allele in the group and taking the fraction out of the whole
Take away message: Evolution is a change in allele frequencies within a population=
Charles Darwin- scientific theorist famous for coming up with mechanism for
evolution to occur
Grew up as a lazy teenager, dropped out of medical school
Embarked on trip around the world in 1831-1836
Observations:
1. Finches had variation in beaks
-Each island had unique species, resembles mainland species
-Thought maybe they were once the same species
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2. Similarity between fossils of extinct species
-Extinct glyptodonts looked like the giant armadillos
3. Offspring overproduction
-Chance of offspring dying before maturation and because environment can only
support so many
4. Competition for scarce resources
-When resources are limited, there is competition
5. Inheritance of traits from parents
Darwin concluded that there is a “struggle for existence” in which organisms who are
better suited to their environment are more likely to survive, reproduce, and pass on
their traits
Through evolution, organisms become better matched to their environment
After years of developing this theory, it was almost scooped by Alfred Russell
Wallace
III. What is natural selection?
Evolutionary process through which the environment favors a phenotype (or a range
of phenotypes) over others, causing the survivors to densify the gene pool with their
traits after reproducing
Natural selection happens if these 3 conditions are met:
1. Variation
2. Heritable
3. Differential reproductive success- some organisms reproduce more than others
Natural selection is falsely refuted due to religion and the realization that humans
are just like every other species (humans are not special)
3 types of natural selection:
1. Directional selection- average changes, curve of phenotype shifts
2. Stabilizing selection- average stays the same, environment favors intermediate
phenotypes and gets rid of the extreme phenotypes
3. Disruptive selection- average changes, environment favors extreme phenotypes
and gets rid of the intermediate phenotypes, can rarely result in deviation into 2
different species
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