Biology Unit 11 - Evolution

EVOLUTION

What is evolution?

• slow adaptations to someone/something, so that they can survive longer

• effective natural selection

Who is Darwin?

• he studied genetics and animals; studied how traits were passed on

• he studied on a isolated island so he could really notice the new traits in animals

DEVELOPMENT OF THE THEORY OF EVOLUTION

Scientific theory: a theory is an explanation of a set of related observations or events based upon proven hypotheses and verified multiple times by a detached groups of researchers

EVOLUTION DUE TO THE PROCESS OF NATURAL SELECTION

What does evolution due to the process of natural selection mean?

• differences in survival and reproduction (you have to be able to reproduce to move along the trait) among individuals due to environmental conditions

What are some environmental conditions that could affect reproductive success?

• climate, predators, habitat, food/water

NATURAL SELECTION IS THE MECHANISM OF EVOLUTION

• interaction between environment & variability within population

• variation by chance

• natural selection NOT chance

FOUR POSTULATES OF NATURAL SELECTIONS

1. Variation

2. Heredity

3. Selective Pressure

4. Reproductive Success

POSTULATE 1 - VARIATION

• individuals within a population vary in their traits

  • genetic variation

  • variations arise by chance from ransom mutations in DNA

POSTULATE 2 - HEREDITY

• some of these variations/traits are hereditable

• traits are passed from parent to offspring

POSTULATE 3 - SELECTIVE PRESSURE

• a population can produce more individuals than can survive

  • resources are limited

  • individuals compete for survival

• in each generation, some survive and others don’t

POSTUATE 4 - REPRODUCTIVE SUCCESS

• individuals with advantageous traits survive and reproduce over time.

• evolution occurs as advantageous traits accumulate

• natural selection selects for organisms that are best adapted to a particular environment (high fitness vs. low fitness)

• survival and reproduction are NOT determined by chance; they are determined by the traits an organism possesses

EVIDENCE FOR EVOLUTION

1 - GEOGRAPHIC DISTRIBUTION

• Looks at geographical distribution of animals and plants.

• Species that are closer in proximity to one another are usually more closely related.

2 - FOSSIL EVIDENCE

• fossil: any part or trace of an organism that is preserved in rock or sediments

• fossils of an ancient species tend to be simpler in form than modern species

• Transitional fossils - fossils or organisms that show the intermediate states between an ancestral form that of its descendants

  

3 - COMPARATIVE ANATOMY

a. Vestigial Organs

• remnants of structures that may have had important functions in an ancestral species, but have no clear function in modern descendants

  

b. Homologous Structures

• Body parts that have the same structural design and origin in different organisms

4 - COMPARATIVE EMRYOLOGY AND DEVELOPMENT

• More closely related species have embryological development that are more similar

5 - CELLULAR AND MOLECULAR EVIDENCE

• closely related species have similar molecular sequences

  

PATTERNS OF EVOLUTION

PATTERNS OF EVOLUTION

(what evolution looks like)

1. divergent evolution

   • one common ancestor evolves into two or more species

2. convergent evolution

   • two distinct species become more similar over time due to similar environments

3. coevolution

   • two species evolve in response to one another

EXAMPLES

divergent evolution →

convergent evolution →

coevolution →

POPULATION EVOLUTION

HOW CAN GENETIC CHANGE HAPPEN IN A POPULATION?

Population Evolution

1. natural selection - not random

2. gene flow - random

   • immigration

   • emigration

3. genetic drift - random

   • bottleneck effect

   • founder effect

4. mutation

1. NATURAL SELECTION

successful organisms are those that have the best adaptations to their present environment

• adaptations = “more fit”

example of natural selection → tuberculosis

• variation → bacteria are resistant or not

• heredity → resistant bacteria pass on trait

• selective pressure → antibiotics

• reproductive success → resistant trait allows bacteria to survive and reproduce over time so whole population can become resistant very quickly

2. GENE FLOW

the movement of alleles from one population to another

• immigration adds alleles to a population → increase genetic variation

• emigration removes alleles from a population → decrease genetic variation

3. GENETIC DRIFT

random changes in allele frequency that happens by chance

2 main causes of genetic drift:

1. bottleneck effect

   • the reduction of a population’s size that randomly changes the distribution of alleles

   • big decrease in genetic variation

2. founder effect

   • occurs when individuals that colonize a new area do not accurately represent the gene frequency of the parent population

4. MUTATION

increases variations in gene pool by randomly creating new alleles

• could be good or bad

THE ROLE OF REPRODUCTION IN POPULATION EVOLUTION

• the sexual reproductive strategy was the most successful because it allowed more genetic variation

• the role of sex in evolution is too create more genetic variation/ diversity so a species can keep up with the environment

• the red queen hypothesis is that species must adapt and create in order to survive

Advantage of producing Asexually:

• you don’t have to find a mate

• guarantied that you will reproduce

Disadvantages of producing Asexually:

• no variation

• accumulate mutation faster in a population

Advantages of producing Sexually:

• variation in offsprings

• weed out harmful mutations

Disadvantages of producing Asexually:

• less efficient- more energy used

• have to find a mate