Y10 Biology

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Brief overview of Charles Dawrin and his trip to the Galapagos islands

Charles Dawrin developed his theory of evolution by natural selection on a trip to the Galapagos islands.

Dawrin’s observations regarding finches on the Galapagos islands

• He noticed that though similar in appearance, the finches varied in body, beak size/shape and behaviour

• Noticed that each species of finches had particular adaptations to its life on its specific island and environment

• Depending on food available, birds with a particular trait were more successful

Define natural selection

Organisms that are more adapted to their environment are more likely to survive and pass on the genes that aided their success. This process causes species to change and diverge over time.

Outline the process of natural selection

OVSASRAC

1. Overproduction

2. Variation

3. Struggle for survival

4. Adaptation

5. Survival of the fittest

6. Reproductive fitness

7. Allele carryover

8. Change to the gene pool (evolution)

OVSASRAC: Overproduction

More young are born than survive to maturity.

OVSASRAC: Variation

Sexually reproducing species show variation in inherited features via:

• random assortment

• crossing over

• random mating

• mutation

OVSASRAC: Struggle for survival

Individuals in a population compete with one another for survival. e.g.:

• competition for resources (food, water, shelter)

• competing for mates

• against predators and disease

OVSASRAC: Adaptation

Species have features that help them survive in their natural habitat

OVSASRAC: Survival of the fittest

Some individuals are better adapted to their environment and are more likely to survive than others.

OVSASRAC: Reproductive fitness

Those who survive longest are likely to successfully raise the most offspring

OVSASRAC: Allele carryover

Offspring that survive will carry the alleles that determine adaptive features

OVSASRAC: Change to the gene pool (evolution)

Alleles that determine favourable features will increase in the gene pool, and unfavourable alleles will decrease.

Discuss the rise of superbugs and the key practices which has led to this issue

Superbugs: Some bacteria carry the alleles that make them resistant to antibiotics due to mutation, genetic variation or another adaptive measure.

Practices that lead to superbugs increasing:

• Misuse of, or using antibiotics too often

When antibiotics are overused/misused, the bacteria that caused said disease are overexposed and produce mutations in attempt to survive.

Know the peppered moths example of natural selection

• Specific trees in Britain were white. Peppered moths had 2 appearances: black and white. White blended in with trees and black stood out, causing their population to decline from the selection pressure of their predators.

• Due to the industrial revolution, trees turned black from soot emissions. Black moths blended in, white now stood out. Predators could easily spot and prey upon the white ones. Their population declined while the black type increased as they survived longer.

• Returned to before as the impacts of the I.R. slowly phased out. (+ white, - black)

Define artificial selection

When humans choose to breed certain characteristics in animals.

→ results stem from human input and not nature’s.

→ 2 types: cross-breeding and inbreeding

Understand the benefits and consequences of artificial selection.

Benefits

• New varieties of organisms created

• Achieve mixture of desired traits in offspring

Consequences

• Lack of genetic diversity

• Genetic mutations

• Ethical issues/exploitation

Differences & similarities between artificial selection and human caused natural selection

Differences

The level of interference of humans

Similarities

Alleles that benefit organisms increase in frequency

Describe process of selective breeding

1: Cross breeding

• 2 different individuals w/ desired traits are separated from the (main) population

• Or, one is artificially inseminated

2: Inbreeding

• Where animals of the same lineage are bred to maintain a particular desirable trait.

Discuss the risks associated with inbreeding

Inbreeding is dangerous for the offspring because genetic variation decreases and the chance for harmful mutation increases. This can lead to birth defects.

Define and state the steps in the process of speciation

Speciation:

A changed/new population can’t breed with the old population

→ Variation, isolation, selection and speciation (VISS)

Process of speciation: Variation

Various different alleles in a species population are produced through:

• random assortment

• crossing over

• random mating

• mutations

Process of speciation: Isolation

The species population is split apart, by physical and/or behavioural separation.

Process of speciation: Selection

A selection pressure acts on the population, leading to those with advantageous traits to survive and pass favourable genes down to offspring. The isolated groups have different selective pressures, and this occurs over long periods of time.

Process of speciation: Speciation

After long periods of time, a new species is formed that can’t breed with the old population.

Compare and contrast allopatric and sympatric speciation

Allopatric

Physical separation (e.g. habitat, geographical barriers - water, mountains)

Sympatric

Behavioural separation, yet still coexisting (e.g. mating/breeding times, diff mating calls)

List the 5 major evidences for evolution.

• Homologous structures

• Analogous structures

• Vestigial structures

• DNA comparison

• Protein analysis

Evolution evidence: Homologous structures

• Structures (bones) with a similar build/architecture
  → e.g. pentadactyl limb (5 fingers/toes) in vertebrates

• Similar structures, diff functions

• Inherited from a common ancestor

Evolution evidence: Analogous structures

• Structures in diff organisms have same function but have evolved independently.

• Not inherited from common ancestor

• Convergent evolution proof (similar ancestry but developed similar traits for similar needs)

Evolution evidence: Vestigial structures

A feature a species has inherited from an ancestor but is now less elaborate and functional than in the ancestor.

→ e.g. appendix, tailbone

Evolution evidence: DNA comparison

• Sequences of bases (ATGC) are very similar in closely related species

• Less similar in distantly related species

• Evolution from common ancestor

Evolution evidence: Protein analysis

• Compares amino acid sequences in proteins from diff organisms

• Similar sequences suggest common ancestor.

Explain how continental drift provides a well supported explanation for the geographical isolation of species that eventually results in divergent evolution

• Continental drift: continents slowly separating over time.

• As they separated, species became geographically isolated.

• Species had to adapt to new surroundings

  • e.g. selection pressures and new enviro.

• Leads to divergent evolution (allopatric speciation)

• Results in speciation

Divergent evolution: accumulation of differences btwn closely related populations within a species, leading usually to speciation.

Describe the similarities during the early stages of embryo development in diff species

Comparative embryology

• Many vertebrae embryos are similar.

• Many have features not present in adult (e.g. gills, tail)

• Common developmental pathway depends on closeness of relationship.

• Evidence of common ancestry.

Identify vestigial structures & explain how they’re interpreted as evidence of an ancestral heritage in which these structures once performed other tasks.

Human appendix: Doesn’t do much now, but used to digest tough plant material.

Pelvic bones in whales: Don’t help with swimming but are leftovers from when ancestors had legs and lived on land.

Account for differences in the frequency of the sickle cell allele in diff regions around the world

→ Explain how malaria is a selection pressure for the sickle cell anaemia allele

Sickle cell anaemia occurs when the gene for haemoglobin mutates into a sickle form (Hb-S), causing a sickle/moon shaped red blood cell. They clog up blood vessels and affect organ function/health. Also less efficient at delivering oxygen.

Malaria is a parasite which destroys normal RBC. It doesn’t destroy sickle-cell shaped RBC. West African population have a selective advantage to possess sickle-cell anaemia.

Account for diff adaptation types

Behavioural

Smth an animal does usually in response to some type of external stimulus in order to survive

→ polar bears hibernating

Structural (physical)

Physical features of an organism that enable them to survive in their environment

→ penguins have blubber to protect them from cold

Functional (chemical/internal)

An internal body process to regulate + maintain homeostasis for an organism to survive in the environment in which it exists

→ temperature regulation (chemical process)