Evidence For Evolution Flashcards
The Fossil Record
- When fossils are arrayed in the order of their age, a progressive series of changes are seen
- Fossil records document the course of life through time
no outliers
evidence of evolution
o Evolutionary change in body size, crown height, molar base expansion, and toe reduction
as you get bigger, you get less toes ie. horses and their hooves
Transitional Fossils
from fishes –> land animals
Tiktaalik: intermediate between fish and land animals
Molecular Record
• The longer organisms have been separated according to the fossil record, the more differences are seen in the structure of their DNA
without errors
there would be no evolution
more mutations between species, the farther apart they in the fossil record
silent mutations in a protein
don’t affect the amino acids and wont change the overall function of a protein
Nonsynonymous (missense) substitutions
do change the amino acid sequence and are likely to have an effect (often deleterious) on protein function; such substitutions are targets for natural selection.
cytochrome c
lack of variation across the sequences at positions 70-80 showing the similarity between organisms
suggests that this region is under strong stabilizing selection and that changing its amino acid sequence would impair the protein’s function
Human Chromosome 2
great apes have 24 chromosomes
humans have 23 chromosomes
reasons we have 23 chromosomes is because great apes evolved and their two chromosomes became one chromosome aka Human chromosome 2
SRGAP2
Humans have four different versions of SRGAP2
primates have just one.
was duplicated in the human lineage about 3.4 mya, resulting in SRGAP2A and SRGAP2B
Further duplications of SRGAP2B gave rise to SRGAP2C about 2.4 mya and to SRGAP2D about 1 mya.
SRGAP2A
SRGAP2A, stimulates the maturation of dendritic spines
SRGAP2C
promotes an increased number of immature spines
might have played a major part in the emergence of the Homo lineage 2-3 mya
This development might have contributed to the evolution of human cognitive abilities.
SRGAP2 MUTATIONS
mutations of the gene in the brain’s neocortex led to complex thought
Ostn genes
found in the muscles and bones of mammals
in humans its also found in neurons and provides clues to how humans evolved their cognitive abilities
opsin gene
tuned to a specific wavelength of light that helps us see different colors
Humans, apes and Old World primates have 3 separate opsin genes involved in color vision.
dichromat
see fewer than 20 color nuances
trichromat
See between 20 and 32 color nuances
tetrachromat
See between 32 and 39 colors nuances
short wavelength opsin gene
found on chromosome 7
all primates have it
medium and long opsin
found on the X chromosome
old world primates have medium and long=tetrochromatic
New world monkeys
mutations in genes that discontinued monkeys from having both medium and long wavelength
female new world monkeys have the potential to be trichromatic because since the medium and long wavelength is found on the X chromosome
male new world monkeys are only dichromatic because they only have one X chromosome meaning they can only be MW or LW
Homology vs Homoplasy
Homology is similarity due to common descent and homoplasy is similarity due to environment not common descent ie arctic: white fur
structural homology
inherited similar structures from a common ancestor
wings
between bats and birds
don’t have common ancestor but due to their environment they have wings
convergent morphology
convergent evolution aka homoplasy
Similar anatomy evolved among lineages that independently adopted marine lifestyles
aka land animals became water animals and all developed fins
Developmental Homology
Developmental similarities reflect descent from a common ancestor
Genetic Toolkit
molecular factors that influence genes
DNA Replication, transcription, and translation
Hox genes
affect body position
can reorder the way organs are developed throughout the body
homeobox
All of the HOM and Hox genes share a 180-base-pair sequence
almost identical in insects and vertebrates
homology
hom and hox genes are similar
they specify the locations of cells in embryos.
Sonic hedgehog
prevents pythons from developing legs all the way
prairie voles
monogamous
display extensive bonding behaviors after mating. These behaviors are mediated by peptides acting as intercellular signals.
When prairie voles mate specific peptides consisting of 9 amino acids are released; oxytocin in females, vasopressin in males.
receptors for oxytocin and vasopressin in prairie voles are highly concentrated in brain regions responsible for attachment
montane and meadow voles
polygamous
there are far fewer receptors for these peptides, and as a result, fewer bonding and caring behaviors.
vestigial structures
structures that you don’t need anymore
aka goosebumps, human tailbone
analogous traits
similarities result from convergent evolution
patterns of distribution
inhabitants of ocean islands resemble forms of the nearest mainland
adaptive radiation
over time, the population diversifies into several distinct species on different islands
biogeographical record
Darwin concluded:
Species arrive on islands by dispersing across the water
Dispersal from nearby areas is more likely than distant sources
Colonizers often evolve into many species
Marine species richness is greater around islands than terrestrial species richness on the islands because marine species are more successful at colonizing island habitats via the water than terrestrial species: no intermediary needed
After arriving at an island, species evolve, leading to the even greater species richness we see in marine species than in terrestrial species
