| What is a clade? | a group of organisms that evolved from one ancestor (node)
clade members have common traits bec of a shared evolutionary lineage |
| How is evidence for which species are part of a clade found? | from the base sequence of a gene or the corresponding amino acid sequence of a protein |
| What are cladograms based on? | structural features (lungs, hair)
or molecular features (sequences, mutations) |
| What are the limitations of using structural characteristics to compare species? (2) | 1) closely related organisms can show very diff features (homologous) bec of adaptive radiation
= rapid divergence to suit ecological niches
2) distantly related organisms can show similar features (analogous) bec of convergent evolution
=common selection pressures) |
| What is convergent evolution? (4) | independent evolution of common characteristics
shard environment = structural similarities
eg: dolphins and sharks look similar but distantly related bec of of same environment
eg: dolphins and cheetahs look different but are closely related bec of diff ecological niches |
| What is the cladogram with monkeys and humans like? (2) | humans, chimpanzees , gorillas, gibbons and orangutans are part of the Hominoids clade
the Hominoids clade is part of a larger clade = the Anthropoids which include new and old world monkeys |
| What types of molecular evidence is used to compare for similarities? | DNA or amino acid sequences
non coding DNA mutates fastest (don't affect protein function)
gene sequences mutate slower ( can change protein structure)
Amino acid sequences mutate slowest (codon degeneracy)
amino acid sequences are used to compare distantly related species
DNA sequences are for more closely related organisms
mitochondrial DNA is used for comparisons within a species (mtDNA) |
| Why are some groups of species reclassified? example? | because of new molecular data
EG: figworts have been reclassified according to their DNA
they examined the chloroplast DNA
= split the species into5 different clades |
| What is molecular clocks? | calculating the time of divergence according to the specific number of mutations as some sequences accumulate mutations at a constant rate
eg: 1 / million years
different genes can mutate at different rates and earlier changes can be reversed later |
