Introduction to Evolution Flashcards
What is Evolution?
- the increase in fitness over time due to natural selection, or adaptation
- the accumulation of mutations, which alter fitness over time
- the change in allele frequencies (or the heritable expression of those alleles) in a population across generations
- the progression into more complex forms of life
What is Evolution?
Change in _____ of genetically different individuals at each generation
proportion
What is Evolution?
Acts by _____ individuals from the population, or by allowing some to ____ __ ____
- removing
- leave more offspring
What is Evolution?
By _____, we are referring to a group of _____ individuals and their _____ (in the case of sexual species)
- population
- interbreeding
- offspring
5 Major Mechanisms of Evolution
- Genetic Drift
- Mutation
- Epigenetic Inheritance
- Migration (Emigration & Immigration)
- Natural Selection
Totally random changes in allele frequency from generation to generation
Genetic Drift
Changes in the genetic code, such as errors in DNA replication, gene deletions or duplications, etc…
Mutation
Heritable changes that are not due to changes in DNA sequence itself, but the expression of the DNA
Epigenetic Inheritance
Alleles moving from one population to another
Migration
- when some alleles favored over others due to an increase in fitness (not random)
- acts on genetic variation in the population
- survival of the fittest
Natural Selection
Natural Selection acts on _____ or _______ variation in a population
genetic or epigenetic
Sources of Genetic Variation
- Mutation
- Epigenetic Inheritance
- Genetic Drift
Sources of Genetic Variation:
Mutation
generates genetic variation
Sources of Genetic Variation:
Epigenetic Inheritance
changes expression of genes
Sources of Genetic Variation:
Genetic Drift
reduces genetic variation
Without ____ or _____ variation, Natural Selection ____ occur
- genetic or epigenetic
- cannot
What are the other Aspects of Biology that Evolutionary Concepts Permeate?
- Biotechnology
- Agriculture
- Medicine
- Conservation
In Agriculture, most of your food is a product of ____ ____ ____, or ____ ____ ____
- intense artificial selection
- human induced evolution
It is an emergent evolutionary changes either on heritable traits or on their genetic and epigenetic basis as responses to direct or indirect pressures imposed by human activities
Human-induced Evolution
Modified Wild Cabbage:
Selection for Terminal buds
Cabbage
Modified Wild Cabbage:
Selection for Lateral buds
Brussels sprouts
Modified Wild Cabbage:
Selection for Stem
Kohlrabi
Modified Wild Cabbage:
Selection for Leaves
Kale
Modified Wild Cabbage:
Selection for Stems and Flowers
Broccoli
Modified Wild Cabbage:
Selection for Flower clusters
Cauliflower
- it is the fastest evolving organism on Earth
- infects macrophages, T-cells
HIV
____ is among the most deadly epidemics in Human History
AIDS
HIV has the ____ ____ ___ of any virus or organism observed to date
fastest mutation rate
HIV _____ more rapidly than humans, and more quickly than the ability of humans to ___ __ ___
- evolves
- produce new drugs
HIV is a _____ with two single
strand RNA genomes
Retrovirus
What is retrovirus?
Reverse
Uses the enzyme ____ ____ to replicate RNA to DNA
Reverse Transcriptase
Reverse Transcriptase is used to _____
replicate RNA to DNA
HIV attacks host ____ ____: infects ______ and ____ ____
- immune system
- macrophages and helper T-cells
How might HIV Evolve?
- Drugs impose Selection on HIV
- Transmission Rate imposes Selection on HIV
- Host immune system also imposes selection on the virus HIV
Drugs impose Selection on HIV:
evolution of drug resistance
Transmission Rate imposes Selection on HIV:
evolution of virulence
Example of an HIV drug
AZT (Azidothymidine)
AZT (Azidothymidine) is a ____ ____ which ____ reverse transcription and ____ viral replication
- thymidine mimic
- stops
- impedes
Why does AZT work initially but fail in the long run?
- Fast Mutation Rate
- Natural Selection
- Tradeoff
FAST MUTATION RATE:
____ of ____ arise, including in the viral reverse transcriptase gene → genetic variation
Lots of Mutations
NATURAL SELECTION favors ____ ____ enzyme mutant that can recognize ___ and not use it
- reverse transcriptase
- AZT
The careful reverse transcriptase enzyme is ___, but the virus is now ______ to AZT
- slow
- resistant
_____ between ___ & ___ vs. ___ & ___ enzyme
- Tradeoff
- fast & sloppy
- slow & careful
Need to keep host alive long enough to get passed on to the next host
Selection on Virulence of HIV
Selection on Virulence:
High Transmission rate
High Virulence
Selection on Virulence:
Low Transmission Rate
Low Virulence
High Transmission rate : High Virulence
- Can grow fast and jump to the next host
- ok if host dies
- the genetic strain that grows faster will win
Low Transmission Rate : Low Virulence
- More virulent strains would die with the host and get selected out
- less virulent strain that does not kill the host will win
High Transmission Rate
Natural selection will favor the MORE virulent strain
Low Transmission Rate
Natural selection will favor the LESS virulent strain
Combating HIV
- Must lower transmission rate of HIV so that less fatal strains evolve
- Must understand evolutionary properties of a disease
Evolutionary properties of a disease
- Evolutionary history
- Mutation rate
- Selective Forces
- Evolutionary Tradeoffs
Evolutionary Tradeoffs:
Evolution in response to drug AZT
slow & accurate vs. fast & sloppy replication
Evolutionary Tradeoffs:
Evolution in response to transmission rate
slow growing & less virulent (keep host alive) vs. fast growing & more virulent
Evolution in Host-Parasite System
SELECTION ON THE HOST (Humans)
- Some humans have resistance to some HIV strains
- Proportion of people with resistant alleles is increasing in some populations
What would happen when AZT therapy stops?
- Back mutations that restore the Amino Acid sequence to the original state are then favored by selection so that reverse transcription could speed up again
____ & ____ are favored – because fast replicating mutants would ____ the slower
- fast & sloppy
- outgrow
What is Evolution?
Leading to an ____ change in characteristics of populations over time
average
Change in allele frequency
genetic composition
Heritable change in the expression of those alleles
epigenetic inheritance
