topic 5: Natural Selection and Evolution
Natural selection is Darwin’s most famous theory; it states that evolutionary change comes through the production of variation in each generation and differential survival of individuals with different combinations of these variable characters. Individuals with characteristics which increase their probability of survival will have more opportunities to reproduce and their offspring will also benefit from the heritable, advantageous character. So over time these variants will spread through the population.
Describe the process of evolution by means of natural selection
image from en.wikipedia.org
Natural selection is the process by which species adapt to their environment. Natural selection leads to evolutionary change when individuals with certain characteristics have a greater survival or reproductive rate than other individuals in a population and pass on these inheritable genetic characteristics to their offspring (Survival of the Fittest). Simply put, natural selection is a consistent difference in survival and reproduction between different genotypes, or even different genes, in what we could call reproductive success.
What happens is:
What happens is:
- A mutation occurs
- If the mutation is beneficial, the animal will survive longer and reproduce more
- Some of its offspring will inherit the mutation
- These offspring will also have better chance of survival, meaning they live longer and reproduce more
- Over a long period of time this process is repeated and gradually the mutation becomes a common gene in a species and those with the mutation become the only ones, as those without cannot compete with those expressing the mutated gene
Describe variation and state that competition leads to differential survival of, and reproduction by, those
organisms best fitted to the environment
organisms best fitted to the environment
Some of the characteristics possessed by an individual in a population can be said to be inherited. These characteristics are passed on as a result of sexual reproduction. Sexual reproduction also introduces an element of randomness, so that variation is brought about in a population. These two almost contradictory factors - dependable inheritance of characteristics from parents, and variation within the population - are essential to an understanding of the process of evolution.
Assess the importance of natural selection as a possible mechanism for evolution
Natural selection is one of the driving mechanisms of evolution. The compelling logical process of natural selection is clear in producing adaptive changes within a species, such that it evolves to be more competitive in its environment.
Natural Selection is often used synonymously with Evolution; however, they have very different meanings. Here are some very important points about natural selection and evolution:
No genetic component à no evolution in response to selection
Natural Selection is often used synonymously with Evolution; however, they have very different meanings. Here are some very important points about natural selection and evolution:
- Natural selection is a mechanism (differential reproductive success due to traits)
- Evolution is a process (change in allele frequencies over time)
- Natural selection is one mechanism that can lead to evolution
- Evolution can also be caused by all of the other forces mentioned here (drift, migration, mutation, nonrandom mating)
- Natural selection may not lead to evolution if the trait under selection is not heritable.
No genetic component à no evolution in response to selection
Determine that evolution is the process of biological change within a population over time
image from www.boundless.com
Evolution is a change in the gene pool of a population over time. A gene is a hereditary unit that can be passed on unaltered for many generations. The gene pool is the set of all genes in a species or population.
Recognize that the theory of evolution is a scientific explanation based on a large accumulation of evidence
image from darwin200.christs.cam.ac.uk
A scientific theory is "a well-substantiated explanation of some aspect of the natural world, based on informational facts that have been repeatedly confirmed through observation and experiment. Theories are formed from hypotheses that have been subjected repeatedly to tests of evidence which attempt to disprove or falsify them. In the case of evolution through natural selection.
The "theory of evolution" is actually a network of theories that created the idea of how organisms evolved. The fossil record is one of the most common evidences given for evolution.
The "theory of evolution" is actually a network of theories that created the idea of how organisms evolved. The fossil record is one of the most common evidences given for evolution.
Define natural selection as the greater chance of passing on of genes by the best adapted organisms
Describe the development of strains of antibiotic resistant bacteria as an example of evolution by natural selection
Key Terms:
|
Darwin
evolution natural selection Origin of Species antibiotics |
selection pressure
selective advantage frequency antibiotic-resistant bacteria |
sickle cell anaemia
population carrier species plasmid |
endosymbion
niche survival mutation overpopulation |
competition
camouflage variation resistance heritable |
Class Materials:
Evidence of Evolution activity
Evidence of Evolution (ppt)
Evidence of Evolution (study guide)
Natural Selection practical
Peppered Moth practical
Sickle Cell Anemia and Genetics Background
Sickle Cell Anemia project
Antibiotic Resistant Bacteria activity (video clips below)
Useful Links:
For more information on the life of Charles Darwin click here.
Check out this video clip on Charles Darwin
Check out this video clip on Evolving Ideas.
PBS Evolution: why sex
The Complete Work of Charles Darwin Online Darwin,
Natural History Museum: Darwin200
Evolution: Darwin's Dangerous Idea: PBS program
The Darwin Correspondence Project
Darwinians and Evolution
BBC: Historic Figures
In The News:
Genetic clue to how limbs evolved from fins from BBC Science
Read the article on Evolution: Fact or Theory.
Scientific America article Origins of Life .
Learning Outcomes:
Video Clips:
Evidence of Evolution activity
Evidence of Evolution (ppt)
Evidence of Evolution (study guide)
Natural Selection practical
Peppered Moth practical
Sickle Cell Anemia and Genetics Background
Sickle Cell Anemia project
Antibiotic Resistant Bacteria activity (video clips below)
Useful Links:
For more information on the life of Charles Darwin click here.
Check out this video clip on Charles Darwin
Check out this video clip on Evolving Ideas.
PBS Evolution: why sex
The Complete Work of Charles Darwin Online Darwin,
Natural History Museum: Darwin200
Evolution: Darwin's Dangerous Idea: PBS program
The Darwin Correspondence Project
Darwinians and Evolution
BBC: Historic Figures
In The News:
Genetic clue to how limbs evolved from fins from BBC Science
Read the article on Evolution: Fact or Theory.
Scientific America article Origins of Life .
Learning Outcomes:
- Describe the process of evolution by means of natural selection
- Understand that many mutations are harmful but some are neutral and a few are beneficial
- Understand how the frequencies of alleles in a population can change as a result of natural selection
- Understand how resistance to antibiotics can increase in bacterial populations
- Understand how natural selection can lead to the formation of new species
Video Clips:
Antibiotic Resistance
Recently, a new strain of Panama disease has attacked bananas in South Asia. Some producers expect the strain to spread throughout the globe. Could this mean the end of the banana as we know it? Join Ben Bowlin as he explores the future of the banana.
