Year 10 Biology Evolution

What is evolution?

The process by which permanent change in the genetic makeup of a population occur as a result of natural selection acting on the genetic variation among individuals

What is the half life of a radioisotope?

The time required for half of the unstable nuclei in a sample to decay

What is reproduction?

The biological process through which surviving indivudals produce offspring and pass on their advantageous traits

What is overproduction?

When organisms produce more offspring than can survive, leading to competition for resources

What is natural selection?

The process in which individuals with traits that make them better adapted to an environment are more likely to pass on their genes to the next generation and thus increase the allele frequency of those advantageous traits in the population over time

How are homologous and analogous structures different?

• Homologous structures: Structures in different species that perform different functions but have common evolutionary origin

• Analogous structures: Structures from different species that perform similar functions but do not share a common evolutionary origin

What is embryology? How is it a form of evidence for evolution?

The study of embryonic development of different species to identify similarities that suggest common ancestry

What are some forms of evidence for evolution?

• Embryology

• Biogeography

• Molecular biology

• Transition fossils

What is biogeography and how does it provide evidence for evolution?

The study of the geographical distribution of species that provides evidence for evolution

What is molecular biology, how does it provide evidence for evolution?

The study of molecular structures that helps identify similarites in DNA and protein sequences among different species and indicate evolutionary relationships

What are transition fossils and how do they provide evidence for evolution?

Remains of organisms that show intermediate characteristics between ancestral and modern species, helping to show evolution over time

What are analoguous structures?

Structures in different species that have similar functions but different evolutionary origins

EG wings of birds and insects

What are fossils and what do they show?

Fossils are preserved remains or traces of organisms from the past

• Fossils provide evidence of evolution, past environments and diets

How are fossils dated?

Fossils are dated using relative and radiometric dating

How are relative and radiometric dating different?

• Relative dating: Compares the age of rock layers

• Radiometric dating: Measuring the decay of radioactive isotopes in surrounding rocks to determine their age

EG Radiocarbon dating measures the remaining amount of the radioactive isotope carbon-14, effective for fossils up to 50,000 years old

What is Darwin's theory of evolution?

Darwin’s theory of evolutions states that species change over time via natural selection, where organisms with heritable, advantageous traits are more likely to survive and reproduce

What are the 5 steps of evolution by natural selection?

VISTA: Variation, Inheritance, Selection, Time, Adaption

What is the first step of evolution by natural selection?

Variation: Individuals within a population naturally have different traits and genetic variations

What is the second step of evolution by natural selection?

Inheritance: Many of these advantageous traits can be passed down from parents to their offspring

What is the third step of evolution by natural selection?

Selection: Environmental pressures force a struggle for surivival, where not all offspring will survive

What is the fourth step of evolution by natural selection?

Time: Over generations, advantageous traits allow certain individuals to successfully reproduce more than others

What is the fifth and final step of evolution by natural selection?

Adaptation: These beneficial traits become increasingly common in the population, helping the species better adapt to its environment

What is the gene pool?

The total combination of all genes (including alleles) present in a population or species

How is microevolution different to macroevolution?

Microevolution: Small-scale changes to the genetic composition of a population or species over time

• Microevolution can eventually lead to macroevolution

Macroevolution: Large-scale changes to genetic composition at or above the species level

• Includes the origin of new species, mass extinctions, and major adaptations

What are the 5 mechanisms of evolution?

These mechanisms explain how populations evolve over generations

1. Mutation

2. Non-random mating

3. Gene flow

4. Finite population size (genetic drift)

5. Natural selection

What are sampling errors and what mechanism of evolution leads to this?

Sampling errors: The distortion of a population's genetic makeup due to chance, occurring when a sample of the population doesn’t exactly represent the larger gene pool.

Mechanism: Genetic Drift

In any finite population, random events determine which individuals breed. The fewer the breeders, the larger the sampling errors can be

What are the bottle neck and founder effects? What evolutionary mechanisms are they caused by?

The bottleneck effect: A sharp reduction in a population's size caused by random events where the surviving group is unrepresentative of the original population, resulting in reduced genetic diversity.

The founding effect: When a small group of individuals breaks away from a larger population to form a new, isolated population in a different area

Mechanism: Genetic drift

The allele frequencies in the population change randomly over generations due to chance rather than natural selection

Mechanisms of evolution: Finite populations (genetic drift)

The random changes in allele frequencies due to chance events rather than natural selection, especially in small populations

Result: Can cause loss of genetic variation and random fixation of traits (not based on survival advantage)

Mechanisms of evolution: Non-random mating

Individuals choose mates based on certain traits rather than by chance

Result: Certain traits become more common (e.g., bright colours, strength), even if not linked to survival

Mechanisms of evolution: Mutations

Random changes in DNA that create new alleles (genetic variation).

Result: Increases genetic variation in a population, providing new traits for selection to act on

Mechanisms of evolution: Gene flow (migration)

The movement of alleles between populations when individuals migrate and breed

Result: Increases genetic diversity within a population and reduces differences between populations

Mechanisms of evolution: Natural selection

Individuals with traits that are better suited to the environment are more likely to survive and reproduce, passing those traits on

Result: Populations become better adapted to their environment over time.

What is adaptive evolution?

The process by which a population becomes better suited to its environment over successive generations due to natural selection

How do humans defy natural selection?

Through technology, medicine and agriculture that allow individuals with less advantageous traits to survive and reproduce

What does survival of the fittest state?

Individuals with traits best suited to their environment are more likely to survive, reproduce, and pass those advantageous traits to their offspring.

Divergent evolution

When two or more populations share a common ancestor but become increasingly different over time due to different environmental pressures

EG Galapagos finches: The birds evolved beaks in different shapes for different food sources

What are some examples of physical barriers that can lead to divergent evolution?

• Erosion

• Continental drift

• Natural disasters

• Migration

• Man-made structures

Convergent evolution

When unrelated species evolve similar traits independently because due to similar environments or selective pressures

EG The wings of bats and birds evolved for flight, or the marine body shape of dolphins and fish evolved for swimming

What does reproductive isolation result in?

The separation of a population that results in them being unable to interbreed, resulting in different species

What is speciation and what is it caused by?

The formation of new species when populations of the same species become reproductively isolated and evolve independently over time

What is a species>

A group of organisms that are closely related and can breed to produce fertile offspring

What is adaptive radiation?

Divergent evolution of a species that results in many different species adapted to diverse environments

What is the difference between divergent and convergent evolution?

Divergent evolution: When species with a common ancestor become different over time due to different environments and selection pressures

Convergent evolution: When unrelated species evolve similar traits over time due to similar environments and selection pressures

What is biological fitness?

The ability of an organism to survive and reproduce successfully in its environment, passing its genes on to the next generation

What is selective advantage?

A trait that helps an organism survive and reproduce more successfully than others in its environment

Result: Advantageous traits becomes more common over time due to selective advantage through natural selection

What are selective pressures?

Environmental factors that affect an organism’s chances of survival and reproduction

Predators, food availability, disease, climate, competition for resources

Selective pressures drive natural selection by giving certain organisms a selective advantage

What does the term allele frequencies mean?

Allele frequency is the proportion of a specific allele in a population’s gene pool.

• It shows how common an allele is compared to other alleles for the same gene

• Written as a percentage or decimal

What is the fossil record and what evidence does it provide?

Fossil record: The collection of all fossils and their position in rock layers

Shows evidence of:

• Evolution over time

• Extinct species that no longer exist today

• Transitional species

What are common ancestors?

Organisms that two or more different species evolved from in the past

What are transitional species?

A species that shows intermediate characteristics between ancestral species and modern species, providing evidence of evolutionary change

EG Early birds with traits of theropod dinosaurs

How does variation in bacteria populations occur?

• Bacteria reproduce very rapidly, leading to a fast rate of DNA mutations.

• Beneficial mutations cause bacteria to survive, reproduce, and pass on the mutation, making it more common in the population over time via natural selection

What is antibiotic resistance?

When bacteria evolve the ability to survive exposure to antibiotics that would normally kill them or stop their growth

How does antibiotic resistance occur and prove useful for bacteria?

• Bacteria have random mutations that make them resistant

• Antibiotics kill non-resistant bacteria, but resistant ones survive and reproduce

Result:

• Resistant bacteria become more common as they reproduce faster and have more resources

• Infections become harder to treat with antibiotics

What are homologous structures?

Structures in different species that have different functions but share evolutionary origins

• Created by adaptive radiation EG Human arm vs whale fin

What are vestigial structures?

Structures in an organism that have reduced purpose but were functional in its ancestors

EG Human tailbone, whale pelvic bones

What are conserved proteins?

Proteins that remain very similar or unchanged across different species over long periods of time because they perform essential biological functions

• EG Haemoglobin, Cytochrome C

What do large differences in molecular homology indicate?

• The species are less closely related evolutionarily

• The species diverged from a common ancestor a long time ago

Key idea: The more differences there are in molecules (like DNA or proteins), the more time has passed since the species shared a common ancestor.

What are homologous proteins?

Proteins that are similar in structure and sometimes function because they share a common evolutionary ancestor

What is molecular homology?

The study of similarities cells at the molecular level

• It shows the evolutionary relatedness of different species through protein sequences