Chapter 25/26 Flashcards
Phylogeny
an evololutionary tree
How is evolutionary history reconstructed?
- fossil record
- comparison of living species
- homologous traits
- analogous traits
- molecular comparisons
- geological time
homologous traits
similar because they wer inherited from a common ancestor
analogous traits
similar, but evolved independently
clade
a grouping that includes a common ancestor and its descendents on a phylogeny tree
forms a nested hierarchy
Eras
Paleozoic, Mesozoic, Cenozoic
Precambrian Era
life arose sometime in this area - 3.5 bya oldest fossils
What is the earliest fossil?
prokaryote
What were the first cells?
protocells
have not been produced in a lab
they are droplets with membranes that have a different internal chemistry than their environment
clay greatly increases the rate of vesicle self-assembly
endosymbiotic theory
explains mitochondria and chloroplasts
eukarote engulfing photosynthetic prokaryote.
Key evidence for endosymbiotic theory
- inner membranes are similar to plasma membranes of prokaryotes
- division is binary fission
- thiese organelles have their own DNA (circular) and transcribe and translate it
- their ribosomes are more similar to prokaryotic than eukaryotic ribosomes
cyanobacteria
photosynthesis adds oxygen to asmosphere
first organism to add oxygen to atmosphere
Eukaryotes
have a cytoskeleton
allows them to change shpae and engulf other cells (get food and digestion)
Horizontal gene transfer
sharing of genes from one cell to another
- most recent common ancestor of all living things
- between mitochondrial ancestor and ancestor of eukaryotes
- chlooplast ancestor and ancestor of green algae
happened a few times with different plastids
advantages of multicellularity
escape from predation, specialization of cells for increased efficiency
single-celled organisms stick together to form colonies
choanoflagellate colony
share common ancestor with animals, but didn’t become animals
unicellular choanoflagellates have the genes for:
collagen, structural proteins in animals
cell adhesion proteins hold cells together
cell communication proteins
Burgess Shale Fossils: Ediacaran Fauna (aquatic)
all common animals started here
(animals in the pre-cambrian period)
Paleozoic Era
Cambrian Period
Evolutionary innovations
gut with 2 openings (allows specialization, can take in more food)
complex nervious system (cephalization - development of head)
shells and exoskeletons (start to see armor)
fish (500mya), amphibians (450mya), reptiles (250mya)
ended with major extinction (90% of all species disappear
Pangea forms
Mesozoic period
“Age of Reptiles”
cone-bearing and flower-bearing plants co-evolved with insects
dinosaurs
homeothermy
vertebrate flight (convergent evolution)
ends with major extinction (50% of all species disappear)
Extinction of Mesozoic
meteorite 10 km across under water
iridium common in meteorites, but not on earth
extinction because a layer cloud of debris blocked sunlight and disrupted climate for several months
volcanic acitivity of Deccan Traps in India
spew lava and ash
CO2 warms the global climate
temp dif between poles and equator slow mixing of ocean water
drop in O2 levels in oceans
select for anaerobic bacteria that prodcue H2S
H2S is toxic and destroys ozone shield
Cenazoic
65mya-today
“Age of Mammals”
adaptive radiation
macroevolutionary changes
Adaptive radiation occurs when:
many vacant niches
major evolutionary innovation
colonized regions with little competition
Macroevolution
a pattern of evolution above the species level
big changes
ex: emergence of terrestrial vertebrates through a series of speciation events, impact of mass extinctions of the diversity of life, and the origin of key adaptatios (like flight in birds)
Mechanisms of Macroevolutionary change
mutations that change the sequence and regulation of developmental genes
Hox genes
Heterochrony
change the relative growth rate or time of different body parts during development
can cause paedomorphosis
paedomorphosis
the sexually mature stage retains juvenile structures of an ancestral species
Evolution is not goal oriented
random mutations cause genetic diversity
complex structures have evoved in increments from simpler versions that were of use to the organism (sometimes for the same function and sometimes for different functions)
exaptation
first used for a different purpose
ex. feathers
Formation of eye
gradual changes can result in complex structureEach stage must provide advantage to organism
The Hox Genes
duplicate the gene
use gene that controls spatial organization of body parts
Homeotic (Hox) genes control identity of appendages by regulating other genes
Idea: major changes in body form can be made by mutations in the regulation of developmental genes not their sequences
each branch point
represents the divergence of 2 species
sister taxa
groups that share an immediate common ancestor
outgroup
outlier of a common ancestor. relative.
used to describe evolutionary relationships
characters shared by the outgroup and ingroup are ancestral characters that predate the divergence of both groups froma common ancestor
stromatolites
3.5bya, still around
layered rocks that from when certain prokaryotes bind think layers of sediment together