4.2.2 Classification and Evolution

Define classification and explain why it is important. (4 marks)

- Classification is grouping organisms based on their similarities.

- It helps scientists identify species and understand evolutionary relationships.

- It allows changes in population size to be monitored over time.

- A universal system ensures scientists worldwide can share and compare data effectively.

what is taxonomy?

the biological practice of classification enables us to arrange species into groups based on their evolutionary origins and relationships

Describe the hierarchy used in the Linnaeus classification system. (4 marks)

- The system is a hierarchy made up of smaller groups placed within larger groups with no overlap.

- Each group is called a taxon (plural: taxa).

- The main levels are Domain, Kingdom, Phylum, Class, Order, Family, Genus, and Species.

- For humans, this is: Eukaryote, Animalia, Chordata, Mammalia, Primates, Hominidae, Homo, sapiens.

Define the term species. (2 marks)

- A species is a group of organisms that can reproduce to produce fertile offspring.

- If offspring are infertile, the parents are from different species and the offspring are classed as hybrids.

Explain the binomial naming system. (3 marks)

- It is a universal naming system to avoid confusion and language barriers between countries.

- Organisms are named using their genus (capital letter) and species (lower case), e.g. Homo sapiens.

- Names are italicised when typed or underlined when handwritten.

State the five kingdoms. (5 marks)

- Prokaryotae

- Protoctista

- Fungi

- Plantae

- Animalia

Describe the key features of the kingdom Prokaryotae. (4 marks)

- Unicellular with no nucleus.

- Cell wall made of peptidoglycan.

- Small ribosomes.

- Autotrophic or chemosynthetic.

Describe the key features of the kingdom Protoctista. (4 marks)

- Mostly unicellular and have a nucleus.

- Some species have chloroplasts.

- May have cilia or flagella.

- Can be autotrophic or heterotrophic.

Describe the key features of the kingdom Fungi. (3 marks)

- Uni- or multicellular with a nucleus.

- Chitin cell wall.

- Heterotrophic, feeding on decaying matter.

Describe the key features of the kingdom Plantae. (3 marks)

- Multicellular with a nucleus.

- Contain chloroplasts and have a cellulose cell wall.

- Autotrophic.

Describe the key features of the kingdom Animalia. (4 marks)

- Multicellular with a nucleus.

- No cell wall.

- Heterotrophic.

- Can move using muscles, cilia, or flagella.

Explain how classification systems have changed over time. (5 marks)

- Early systems relied on observable characteristics, which could be misleading.

- Advances in immunology and genome sequencing improved accuracy.

- DNA base sequence comparisons reveal how closely related species are.

- Amino acid sequence comparisons in proteins like cytochrome C also show relatedness.

- Carl Woese's three-domain system (Bacteria, Archaea, Eukaryota) is based on rRNA and membrane structure.

Describe the phylogenetic system of classification. (3 marks)

- Groups organisms according to evolutionary relationships and origins.

- Shows species' descent from common ancestors.

- Represented by phylogenetic trees, often based on genetic and fossil evidence.

Explain Darwin and Wallace's contribution to the theory of evolution. (5 marks)

- Both developed the idea of natural selection.

- Darwin studied finches on the Galapagos Islands, noting beak shape matched food sources.

- Birds with suitable beaks survived and reproduced, passing on the trait.

- Wallace reached similar conclusions and sent his ideas to Darwin in 1858.

- They published their findings together, and Darwin later published On the Origin of Species.

Describe the main forms of evidence that support the theory of evolution. (5 marks)

- Fossils show preserved remains or traces of organisms from the past, revealing how life forms have changed over time.

- The fossil record demonstrates changes in species' anatomy and the development of more complex life forms from simpler ones.

- DNA base sequence comparisons allow scientists to see how closely related species are and estimate when they shared a common ancestor.

- Amino acid sequence comparisons in proteins such as cytochrome C provide molecular evidence of relatedness.

- Similarities in molecular data support Darwin's theory of common ancestry.

Define intraspecific and interspecific variation. (3 marks)

- Interspecific variation is the difference between members of different species, such as body coverings or feeding methods.

- Intraspecific variation is the difference between members of the same species, caused by different alleles of the same genes.

- This variation is introduced through mutations, crossing over, independent assortment, and random fertilisation.

Explain continuous and discontinuous variation. (4 marks)

- Continuous variation involves traits influenced by many genes and the environment, with a full range of values shown in a line graph or histogram.

- Discontinuous variation involves traits controlled by a single gene, producing distinct categories shown in a bar chart.

- Environmental factors can also create variation, such as scars or tattoos in humans.

- Continuous variation is influenced by both genetics and the environment, whereas discontinuous is determined mainly by genetics.

Describe the three types of adaptations with examples. (4 marks)

- Anatomical adaptations are structural features, e.g. spikes on a hedgehog.

- Physiological adaptations are internal processes, e.g. hedgehogs hibernating in winter.

- Behavioural adaptations are actions taken by organisms, e.g. hedgehogs curling up when threatened.

- All types of adaptation increase an organism's chance of survival in its environment.

Explain convergent evolution with an example. (3 marks)

- Convergent evolution occurs when unrelated species evolve similar features due to similar selection pressures.

- For example, the marsupial mole in Australia and the placental mole in America have similar adaptations despite evolving separately.

- Similar environments can lead to similar traits even in unrelated species.

Explain the process of natural selection. (6 marks)

1. Random mutations occur in a population, introducing genetic variation.

2. Some mutations produce alleles that give an advantage in survival.

3. Selection pressures favour individuals with advantageous alleles.

4. These individuals have a reproductive selective advantage and greater reproductive success.

5. Over generations, the frequency of the advantageous allele increases in the population.

6. Evolution is the change in allele frequency over time.

Describe an example of natural selection in action. (3 marks)

- Antibiotic resistance in bacteria occurs when a mutation produces an allele for resistance.

- In the presence of the antibiotic, resistant bacteria survive while others die.

- Resistant individuals reproduce, passing the allele to future generations.