evidence of relatedness - unit 4 AOS 2

Question 1

structural morphology

Answer 1

• the evidence pf physical structures to determine the relatedness of species

Question 2

homologous structures

Answer 2

• Homologous structures are physical features in two species which can look and function very differently but indicate that they have a common ancestor.
• Homologous structures are physical evidence of divergent evolution, the evolutionary process where two or more populations of a single species accumulate enough genetic differences to be classified as different species
• the differences in how homologous structures are used reflects evolutionary divergence where species have adapted to different selection pressures over time.

Question 3

analogous structures

Answer 3

• features present in two or more species
  that fulfil the same function but do not originate from a common ancestor
• Analogous structures are evidence of convergent
  evolution in which two or more distantly related species (without a recent common ancestor) can be seen to have independently evolved similar traits to adapt to similar environments and selection pressures
• It may occur when different species occupy the same habitat and are thus subjected to the same selection pressures. The shared conditions cause common adaptations to be selected in different species, resulting in structural similarity
• they reveal how different species can adapt in similar ways to similar environments or challenges.

Question 4

Vestigial structures

Answer 4

• vestigial structures are features that have lost all or most of their usefulness as a result of evolution
  by natural selection
• These anatomical features are called vestigial structures and demonstrate the evolutionary divergence of a species from a past activity
• The presence of a vestigial structure indicates that a species has descended from an ancestor in which the structure was functional.

Question 5

molecular homology

Answer 5

• the study of the similarities in the nucleotide
  sequences of DNA or amino acid sequences in proteins between organisms to establish relatedness

Question 6

amino acid sequence similarity

Answer 6

• Amino acid sequences of similar proteins may be used for comparison to see how related species are
• by aligning amino acids sequences for a specific protein (like cytochrome C or hemoglobin), we can observe ow many differences exist.
• fewer differences means closer relatedness.
• over time, mutations occur in DNA, leading to changes in amino acid sequences. by studying the rate and type of mutations, scientists can estimate how long ago two species diverges from a common ancestor.
• it will result in the slowest rate of change due to codon degeneracy. multiple codons can code for the same amino acid, reducing the effect of mutations making the amino acid sequence change over time slower

Question 7

DNA similarity

Answer 7

• sequences of DNA can be compared by looking at the nucleotides between different organisms
  -The number of differences between comparable base sequences demonstrates the degree of evolutionary divergence
• A greater number of differences between comparable base sequences suggests more time has past since two species diverged
• Hence, the more similar the base sequences of two species are, the more closely related the two species are expected to be

Question 8

comparison

Answer 8

• DNA sequencing can detect small mutations, even ones that don’t change the amino acid sequence
• amino acid comparisons can miss evolutionary changes that don’t alter the proteins structure