Biology Evolution SCI

Evolution

mechanisms that drives Change in the inherited characteristics (allele frequencies) of populations over generations.

What is biodiversity, and what are its three types?

• Biodiversity: Variety of life on Earth.

• Genetic: Variety of genes and alleles within a species.

• Species: Variety of species in an ecosystem.

• Ecosystem: Variety of ecosystems in an area.

How is biodiversity a result of evolution?

Evolution creates genetic differences and can produce new species over time, contributing to genetic, species and ecosystem diversity.

Why is maintaining genetic diversity important?

provides variation, helping populations adapt to environmental changes and diseases. Low genetic diversity increases extinction risk

What is variation, and why is it important in evolution?

Variation- diffs between individuals of the same species. allows natural selection to favour individuals with advantageous inherited characteristics, which are passed to offspring.

Genes, genotype and phenotype – Define each term.

• Gene: section of DNA containing instructions for a characteristic.

• Genotype: genetic makeup of an organism.

• Phenotype: observable characteristics of an organism, determined by its genes and environmental factors.

Sources of variation – What causes genetic variation?

• Independent assortment: chromosomes separate independently during meiosis.

• Crossing over: homologous chromosomes exchange DNA sections.

• Mutation: changes in DNA create new alleles.

What is a mutation, and why is it important to evolution?

a permanent change in DNA. can occur spontaneously during DNA replication or be caused by factors like chemicals and radiation. Most are harmful or have no effect, but some can be beneficial. Mutation is the only source of new genetic variation, and mutations in gametes can be passed to offspring.

Environmental factors – How can the environment affect phenotype?

can influence an organism's observable characteristics and genes. individuals with similar genotypes may develop different phenotypes depending on environment.

Population, gene pool and allele frequency – Define each term.

• Population: individuals of the same species living in a particular area at a particular time.

• Gene pool: all the genes and alleles present in a population.

• Allele frequency: how common a particular allele is within a population's gene pool.

What is the relationship between a gene pool and allele frequency?

gene pool contains all the alleles within a population. Allele frequency describes the proportion of each allele in that gene pool. Evolution occurs when allele frequencies change over generations.

What are selection pressures? Give examples.

Selection pressures are environmental factors that affect an organism's ability to survive and reproduce. Examples include predators, competition for food and water, disease, temperature and natural disasters.

Natural selection – What is natural selection, and what are the steps involved?

process individuals with favourable characteristics more likely to survive and reproduce, passing characteristics to offspring.

• Variation exists within population.

• Selection pressures create competition.

• Individuals with favourable traits survive and reproduce more.

• pass these alleles to offspring.

• Favourable alleles become more common over generations.

How does natural selection cause antibiotic resistance in bacteria?

• Some bacteria have mutations that make them resistant to antibiotics.

• Antibiotics kill non-resistant bacteria.

• Resistant bacteria survive and reproduce.

• Resistance alleles become more common in the population.

How does natural selection change a population's gene pool?

Individuals with advantageous inherited characteristics are more likely to survive and reproduce. They pass their alleles to offspring, increasing the frequency of those alleles in the gene pool over generations. Less advantageous alleles may become less common.

What are the four main mechanisms that can change allele frequencies in a population?

• Natural selection: advantageous alleles become more common because their carriers reproduce more successfully.

• Mutation: changes in DNA introduce new alleles.

• Gene flow: alleles move between populations through migration and breeding.

• Genetic drift: allele frequencies change randomly, particularly in small populations or after major events.

How does natural selection produce adaptations?

adaptation- inherited characteristic that improves organism's ability to survive and reproduce in its environment. Natural selection increases frequency of advantageous adaptations over generations. Examples include differences in colour, size and resistance to antibiotics or pesticides.

Why can the same species develop different characteristics in different locations?

Populations in different locations may experience different environmental conditions and selection pressures. Natural selection favours different characteristics in each environment, causing populations to become increasingly different over generations.

What is artificial selection?

Artificial selection occurs when humans choose organisms with desirable characteristics to reproduce. Over generations, these selected characteristics become more common in the population.

eg- Chickens bred to produce more meat or larger eggs.

What is the difference between natural selection and artificial selection?

Natural selection occurs when environmental pressures favour organisms with advantageous characteristics. Artificial selection occurs when humans choose organisms with desirable characteristics to reproduce. Both change the characteristics of populations over generations.

What is the difference between a species and speciation?

• Species: organisms that can breed naturally and produce viable (living) and fertile (able to reproduce) offspring.

• Speciation: the formation of new species.

How does speciation occur?

• A population becomes separated, often by a geographical barrier.

• Gene flow between the populations stops or decreases.

• Different environmental conditions create different selection pressures.

• Mutations and natural selection cause genetic differences to accumulate.

• Eventually, the populations may become reproductively isolated and unable to produce fertile offspring together.

How can geographical isolation lead to speciation?

when a physical barrier, such as a river, mountain or ocean, separates populations. This prevents them from interbreeding and stops gene flow. Over time, different mutations and selection pressures can cause the populations to become separate species.

What are the four main types of evidence that support the Theory of Evolution?

• Fossils

• Biogeography (geographical distribution)

• Comparative anatomy

• Comparative DNA

What is a fossil?

fossil is the preserved remains, impression or trace of an organism that lived in the past. Examples include bones, footprints and impressions.

fossilisation – What requirements help fossils form?

• The organism must be rapidly buried by sediment, protecting it from decay and scavengers.

• More layers of sediment build up, creating pressure.

• Minerals enter or replace the hard parts of the organism, helping preserve them.

• Fossils usually form in sedimentary rock. Hard parts, such as bones and shells, are more likely to fossilise than soft parts.

Fossils – How do fossils support the Theory of Evolution?

provide evidence of organisms that lived in the past and show how life has changed over time. Comparing older fossils with more recent organisms shows that species have changed, new species have appeared and others have become extinct.

How does comparing DNA between species support evolution?

Species with more similar DNA sequences are generally more closely related and share a more recent common ancestor. Mutations cause DNA differences to accumulate over generations.

What are Homologous structures

Structures with similar underlying anatomy inherited from a common ancestor, although they may have different functions.

How does the pentadactyl limb support evolution?

Many vertebrates have a similar underlying limb structure with five digits, including humans, bats, whales and horses. This suggests they inherited the structure from a common ancestor, but their limbs adapted to different functions.

Vestigial organs – What are they? Give examples.

structures inherited from ancestors that have lost their original function or have little current function. They provide evidence of evolutionary change.

Eg

• human appendix.

• Pelvic bones in whales.

Embryology – How does it support the Theory of Evolution?

Species that share a common ancestor often have similar early embryo stages. Features such as tails and gill-like structures suggest they inherited similar developmental patterns, providing evidence of common ancestry.

Biogeography – What is it, and how does it support the Theory of Evolution?

Biogeography is the study of the geographical distribution of organisms, both living and extinct.

supports evolution because the locations of organisms and fossils can reveal common ancestry and how species have changed and spread over time. For example, similar fossils found in different regions can provide evidence of how species were distributed as continents moved.

what ethical issues should be considered when studying heritage sites and artefacts on Country?

• Respect Aboriginal and Torres Strait Islander cultural heritage.

• Protect sites and artefacts from damage.

• Consider the ecological impact of research on the environment.

How does comparing protein sequences support evolution?

DNA codes for proteins. Comparing amino acid sequences shows evolutionary relationships. More similar protein sequences generally indicate a more recent common ancestor.

How can isolation and natural selection lead to different species? Give examples.

• Galápagos finches: populations developed diff beak shapes suited to different food sources.

• Australian marsupials: isolated populations diversified and developed adaptations suited to different environments and ecological roles.

How does speciation occur through evolution? (6 marks)

• Variation: Individuals within a population have different inherited characteristics.

• Separation: A geographical barrier isolates populations, preventing gene flow.

• Selection pressures: Different environments create different selection pressures.

• Favourable traits: Individuals with advantageous traits are more likely to survive and reproduce.

• Inheritance: They pass favourable alleles to offspring, so these traits become more common over generations.

• Speciation: Genetic differences accumulate until populations become reproductively isolated and can no longer produce fertile offspring together.