Please enable JavaScript.
Coggle requires JavaScript to display documents.
Chapter 24- 25 - Coggle Diagram
Chapter 24- 25
The history of life on earh
how the fossil record documents the history of all life
fossil record
Sedimentary rock is the richest source of fossils
Fossils record based on the sequence in which fossils accumulated in the strata
THe deeper the fossil the older it is
Paleontologists study fossils to coe up with story of the earth
Fossils not found n the strata can also be good information
insects frozen in amber
mammals frozen in soil
can help uncover history of things without hard part
how fossils show changes in earths species
Organisms of the past are not like organisms now
Many past organisms are now extinct
Fossils show how new organisms came from old ones
Limitation of fossils
Incomplete chronicle of evolution
organisms did not die in the right place ot time to become fossils
Fossils favor animals with hard parts over squishy ones
places without mud cannot make fossils
many fossils are destroyed by geologic processes and only a fraction have been discovered
How fossils are dated
Radiometric dating
base on radioactive decay of isotopes
uses half life of various elements to measure the age of fossils
Carbon 14 has a half life of 5730 years
by studying the ratio between elements like carbon 14 and nitrogen 14 in fossils we can estimate their age
carbon dating cannot be used for fossiles over 70k years old
different elements are used because of their longer half life
Geologic record
Hadean period (no life) 4500-4000million years
Archean era ( first prokaryotes) 4000-2500million years ago
Neo proterozoic era ( first eukaryotes and multi cellular life) 2500-541 million years ago
Paleozoic era (cainbrian explosion and first terrestial life ) 541-252
Mesozoic era (age of the dinosaurs) 252-66million years ago
Cenozoic era (age of the mammals) 66-0.1 million years ago
Origins of new groups (Ex: mammals)
synapsid (300mya)
multiple bones in jaw
singe pointed teeth
hinge made by articular and quadrate bones
tempora fenestra (hole that probably had powerful cheek muscles
tempora fenestra eventually moved father from the hinge (making the jaws more powerful
Therapsid (280mya)
large dentary bones
long faces
specialized teeth
Large k9s
Early cynodont (260mya)
Dentary was the largest bone in lower jaw
the tempora fenestra finally moved away from jaw hinge (forward of the jaw hinge)
Later cynodont (220mya)
teeth with complex cusp patterns
lower in upper jaw hinge in separate locations
very late cynodont (195mya)
in some mammals original quadrate hinge was lost
only dentary squamosal hinge was left
articular and quadrate bones migrated to the ear region
the new bones in ear area later become the hammer and anvil bones of the ear
Key events in life's history
first single celled organisms
first evidence of single celled prokaryotes dating from 3.5 billion years ago found in stromatolites
prokaryotes ruled the earth for 1.5 billion years (until cambrian explosion)
Oxygen revolution
photosynthetic bacteria (similar to cyano bacteria) started producing oxygen
caused the first mass extinction because other bacterias did not like oxygen
Oxygen started binding with iron in the ocean, precipitating and making layers of banded iron. (most of our iron ironically came from cyano bacteria killing things)
after all the iron precipitated at the bottom of the ocean, the oxygen started saturating the ocean and the oxygen finally started leaking into our atmosphere
Diverse adaptations regarding celullar respiration evolved as a response to changing atmosphere
First eukaryotes
Oldest accepted fossils of eukaryotes are from 1.8 billion years ago
originated from symbiosis when a prokaryotic cell ate another small prokaryotic cell and decided to keep it as a pet ( later becoming the mitochondrion (endosymbiotant)
the host cell who was an anorobe may have benfited from the small cell that used oxygen (over time becoming inseperable)
FIrst host hell (ancient prokaryote)
in folding of plasma membrane, then forming of nucleus
ancient prokayote swallows aerobic heterotrophic bacteria and keeps it
procaryote with early mitochondria swalllows a photo synthetic bacteria (early chloroplast
new prokaryote with nuclear envelop, nucleus, mitochondria and plastid, later goes on to become early photosynthertic eukaryote
increase in diversity of eukaryotes
evolution of more complex eukaryotic cells lead evolution of greater morphological divercity
many eukaryotes differered in chape and size which continues to this day
Origin of multi cellular organisms
Early multi cellular prokaryotes emerged 1.3 billion years ago
earliest taxonomically resolve fossil of multi cell eukaryote was 1.2 billion years ago
larger multi celled eukaryotes dont appear until 600 million years ago
Canbrian explosion
An explosion where suddenly we see most present day animal phyla in our fossil record
Sudden emergergence of predators and new hard parts used for protection and hunting
Took place 530 million years ago
Colonization of land
took place about 5000 million years ago
Adaptations made it possible to eat, reproduce on land and not dehydrate
Early plant fossils show early signs of adaptations regarding internal vascular system and water proof coating to prevent loss of water, still seen in plants today (early plants 400mya lacked true roots or leaes)
in as little as 40million years plants diecified greatly now having root and leaves
the first animals Arthropods (particularly insects ad spiders) were among the first to colonize land, roughly 450 million years ago
earlies tetrapod fossils were found and roughly 360 million years ago ( appear to have evolved from group of lobe finned fishes)
Earliest divergence of humans was about 6-7 million years ago with the first of our species originating only about 195,000 thousand years ago
How the rise and fall of groups of organisms reflect differences in speciation and extinction rates
The earth is marked by periods of rising and falingl of groups
Anaroebic bacteria rose and fell as oxygen concentration when up
The first tetrapods arouse from sea and gave rise to several new groups of organisms
Species divercity goes up if more new species originate then go extinct
these rise and falls help explain the the history of life .The thriving of one group often comes at cost of another helping us understand more extinction rates
THeory of plate tectonics
the earth has formed super continents 3 times
1billion years ago
250 million years ago
600 million years ago
Each time super continents form they break up again in new arrangements
Continents are parts of great plates that move on top of the earth's mantle
movements cause by convection of lava cause plates to shift over time
movement of continents is called continental drift
only move a couple cm per year
Based on earths movements geologists can infer past continent locations
As the earth moved the relative location of north to rocks changed
Using magnetic signal imprinted on rocks you can infer where they were
the direction of magnetic north recorded on rocks does not change
Geologists believe new super continent will be formed in 250 million years
Movement of plates causes earth quakes islands and mountains
locations where plate converge can form mountains (Himalayan mountains)
locations plates slide past each other can cause earth quakes (like the San Andreas fault
Consequences of continental drift
Cummulative effects are dramatic
Alters habitats of organisms
Most species lived in shallow water at the time
The formation of pangea drained shallow areas killing alot of early species
Formation of Pangaea greatly altered physical environment and climate
Extinction of one species can give rise to more species
Shift in continent location can change climate (Ex: Canada used to be in the tropic area of earth and now is up north, changing the climate)
organisms either adapt or go extinct
Promotes allopatric speciation (geographic isolation)
species that were once in the same are might become separated over time
species might start to branch off and speciate
Australia, Asia, South America and Antartica were once connected and had marsupials, however after they broke apart Australia was set afloat and marsupials divercified and placental animals died off
Mass extinctions
5 mass over the last 500million years
end-ordovician- 440mya due to drop in sea level
late devonain- 350 mya
Permain (largest)- 250mya
wiped out 96% of marine species
wiped out 8 of 27 orders of insects
occured in less than 500 thousand years
Caused by extreme episode of volcanism
End of triassic 220mya
creaceous- 66mya (wiped out dinosaurs)
killed half of marine life and many terrestial animals
Evidence of meteor collision, thought to be in Chicxulub crater off the cost of mexico ( crater has the right theoretical size, and is thin layer of enriched iridium in clay)
caused by massive meteor
Dust cloud caused by meteor extinguished most life by blocking suns rays and dropping temperature
Could 6th extinction be on the way
could be under way due to humans destruction of habitats
Introduction of invasive species
Over harvesting
climate change
Consequences of Mass extinctions
Reduce ecological communities
Loss of evolutionary lineages
Evolutionary paths changed forever
Long recovery times for divercity
Changing types of organisms residing in ecological communities
change in abundance of pradators or prey
increased competion for predators and increasd risk for prey
Adaptative radiation
Fossil record divercity increased rapidly due to adaptive radiation
happened after each major extinction
single lineage rapidly speciates to fill out ecological rolls in their community
Worldwide adaptive radiation
Massive adaptive radiation after crestaceous extinction
Out competition and predation kept early mammals small in size and with little divercity
After dinosaur extinction mammals expanded greatly and filled roles occupied by dinosaurs
History of life greatly effected by episode of adaptive radiation including the rise of photosynthetic organisms, large predators following cambrian explosion, and radiation following the colonization of plants
Regional adaptive radiation
radiation over more limited areas
can happen when animals move to distant location with little competition
Ex: Hawaiian archipelago, each island starting naked and being populated by stray organisms despite being 3500km away from land
each island has plenty of diversity between species due to differing soil types, elevation, and levels of rainfall. causing great opportunities
Evolution is not goal oriented (only orientated towards survival in the environment)
Evolution does not have the goal it does not have a perfect organism in mind (not to mention trade offs)
Evolution only priorititizes srvival in the current environment
Evolutionary trends
Animals do not evolve in straight lines
Ex: horses if you look at a horse and wonder where it came from you might be able to trace back a succession of intermediate animals between modern day horses and there ancient ancestor, however when looking at the fossil record all known fossil horses today patterns vanish
Tracking evolution by looking at a single animal is foolish ( its like describing a bush from only looking at one branch and taking it to the root)
Modern day horses are only "one surviving twig from an evolutionary tree that is so branched that is is more like a bush"
The modern genus Equus is a result of several speciation episodes including adaptive radiation
Not all speciation of led to large one toed horses
Species can under go species selection
certain species that used to do good in their environment are now extinct
Many branching species may have been eliminated or selected against in the history of the earth
Evolution does not set out to improve or obtain features, the improved features are just a bi product of survival
Conditions of early earth made life possible
how it started (according to science
abiotic molecules come together to make small amino acids and nitrogeneous bases
these small polymers somehow got together to make polymers
somewhere along the way these polymers were lumped inside of a cell ( we don't know where the lipids came from)
these molecules became self replicating
Synthesis of organic compounds on early earth
planet formed 4.6 billion years ago
for the first 600 million years the eath was inhabiatble
it was constantly bombarded by meteors
the heat caused by meteors prevented and lakes and seas to form to form
the first atmosphere was created
the earth was very hot and the atmosphere had alot of CO2 methane nitrogen and ammonia
as the earth cooled water vapor condensed into oceons
2 people (A. I Oparin and J. B. S Haldane) hypothesized origin of organic molecules
earths early oceans were a primitive soup of organic molecules
energy for such reactions could come from UV light or lighting
earth was electron adding atmosphere ( organic compounds could be created from simple molecules)
Stanly miller and Harold Urley support Haldenes hypothesis
By creating laboratory conditions similar to the those scientist thought the earth would have at the time they created amino acids
Evidence suggesting earth did not have reducing reaction lead to test being performed in neutral atmosphere
they were able to produce organic molecules despite not having reducing atmosphere
Life may have started near volcanoes or vents
small pockets of early atmosphere in volcanoes may have been reducing
they found numerous amino acids forming under conditions similar to volcano eruptions
Hydrothermal vents: vents on the ocean floor that spit out the earth's insides and hot water may have been a place were life could start, but some of get too hot for organic molecules to be stable
Alkaline vents: release water at high ph and warm( may have been more suitable for origin of life)
Abiotic synthesis of macro molecules
a 2016 study demonstrated abiotic synthesis of 2 RNA purine bases Adenine and guanine
Polymers formed spontaneously from dripping solutions of amino acids or RNA nucleotides into hot sand clay or rock
Cytosine and uracil was later discovered in 2009
formation of Protocells
DNA replication need enzymatic machinery and abundant supply of nucleotides
protocells must have had both conditions in order for cell replication to happen
Necessary conditions met by proto cells may have been met in vesicles
fluid filled comparments enclosed by a membrane like structure
they can form spontaneously when lipids are added to water
can exhibit certain properties of life like simple reproduction metabolism and maintenance of different chemical environment inside compare to environment
adding soft mineral clay from volcanic ash speeds up vesicle making process
can grow without dilution
Can absorb the soft mineral clay where RNA and other organic molecules could be attached
Some experiments show vesicles have semi permeable bi layer and can perform metabolic reactions which are necessary for life
Self replicating RNA
the first genetic material was likely RNA
It can act as an enzyme like catalyst (ribosomes)
molecular natural selection lead to some ribosomes being able to self replicate
small RNA molecules can replicate and store genetic information about the vesicles carriers
Vesicles with self replicating catalytic RNA would have an advantage over other vesicles
if a vesicle could grow and split its daughter cell would be a protocell
Protocells likely only had llittle genetic information
Inherated characteristics could have been acted on by natural selection
Most successful protocells would have increased in number
proto cells could properly eploit resources and pass on traits to next generation
If RNA sequences appeared more changes could be possibe
RNA could provide template of which DNA nucleotides assembled
DNA is more stable and capable of replicating more accurately
Major physical changes can happen from changes in gene sequences or regulation of genes
Effects of developmental genes
Genes that alter rate, timing and spatial pattern of change drastically change an organisms form as it develops into an adult
Changes in rate and timing
Organism's shape depends on the growth rates of different body parts
change in rate and timing of developmental events change adults form substancially
Ex: increase growth rate in finger bones lead to wings for bats
Paedomorphosis:
acceleration in sexual maturity leads to species still having juvenile structures from ancient species despite being sexually mature
Example: Most salamanders go through a metamorphosis when entering adult hood but some fully sexually mature despite having juvenile features like gills
Evidence shows that a change in a single locus was probably sufficient to bring padeomorphasis in the axolotl salamander
axolotls, if in the right conditions can maintain their juvenile state and never transform
this change can cause a massive appearance difference compared to ancestors, despite the organisms being genetically similar.
Changes in spatial pattern
Homeopathic genes determine where features like legs and wings will develop
hox genes provide positional information in animal embryo
this information prompts cells to grow into structure appropriate for location
change in these genes can greatly alter physical apperance
In crustaceans changes in the location of where 2
Hox
genes are expressed can be the difference between swimming appendages and feeding appendages
Changes in homeopatic genes like Mads box can produce flowers drastically different in form
Changes in gene sequence
changes in gene sequence can either suppress or express different features
Ex: divergence of 6 legged insects from crusteceans
Hox gene ubx suppresses leg formation where it is expresed
by genetically engineering fruit flies with a hybrid Ubx gene of both fruit fruit flies (Drososophila) and a crustean (shrimp artemia) they were able to determine the exact amino acid changes responsible for the suppression of additional libs in insect.
Changes in gene regulation
can be limited to one cell type
change in regulation of a gene may have fewer harmful side effects than changing sequences
Changes in form of organisms can be from mutations that effect regulation of developmental genes and not sequences
Research results on stickle back show clear and detailed examples of how changes in gene regulation can alter the form of individual organisms and lead to evolutionary change in populations
Evolutionary novelties
evolution makes novel useful structures because they are useful thte one who has them
How could the eye gradually form if a partial eye likely wasnt useful?
Some organisms rely on very simple eyes like some flat worms that have eyes spots to tell if they are being covered or not
If a simple eyes were useful it could eventually have gradual improvements over time
like first evolving reaction to light
a cup shape to tell where light is coming from
Development of a pin hole to prevent overlapping of light rays that may cause image blurriness
Development of early lens, to focus light
complex camera and lens type
How are new species created
Ways to determine new species?
BIological species concept
Based on reproductive isolation
If members of a population stop reproducing with each other they may start to diverge based on environmental or geographic factors
Reproductive barriers stop members of a population from having sex
Members of a population in the same species can have babies but cannot have healthy fertile babies with members of other species
Mambers of a species are united by being reproductively compatible
Gene flow has to be reduced for speciation to occur (members of of the same species transferring alleles to each other and keeps them closely related)
Limitations of biological species concept
species that dont reproduce sexually. Ex: bacteria
Fossils (you cannot tell what can mate with what)
Morphological species concept
classifies species based on shape (physical traits)
Pros: it works asexual and sexually reproducing organisms
Cons: it relies on subjective criteria so scientists may disagree with each other
Ecological species concept
Classifies species based on how they interact with living and non-living parts of their environment
Pros: it can accommodate asexually reproducing species
Cons: Scientist can take advantage of this to claim the found new species
Types of reproductive barriers
Pre zygotic (prevents a zygote from forming)
Gametic isolation: gametes either cant fertilize the egg or cannot survive in females reproductive tract
Mechanical isolation: physically cannot have sex Ex: snails with different coils or a big dog with a spall one
Behavioral isolations: if females don't like your mating ritual then you cant mate but if a female does like it the offspring will likely like that same behavior too
Temporal isolation: species may be in the same area but do not breed because their mating season is different
Habitat isolation: members of the same species occupy different habitats within the same area which leads to them barely interacting with each other if at all
Post zygotic (happens after zygote is formed)
Reduced hybrid fertility: vigorous offsping may occur Ex: (mules and jennies) but the offspring of the 2 species cannot reproduce with other offspring with the same parents
Reduced hybrid viability: fertilization between to species occurs but the genes of the parents impair the hybrids survival
Hybrid break down: the offspring between 2 species may be fertile and viable but the offspring of the hybrid suffers (whether it be with the parent species or another hybrid)
Types of speciation
Allopatric speciation (other country)
population gets divided into geographically isolated sub populations, disrupting gene flow
differences in environment can cause species to diverge due to mutations, natural selection and genetic drift
Snapping shrimp
The isthmus Panama connects both south and North America (there is no longer space between for species to travel across)
Different environments cause divergence and eventually speciation
Populations of shrimp get divided on different sides
snapping shrimp:15 pairs of snapping shrimp have sister species on the other side of the Panama canal . probably because before
Maltose and starch flies fruit flies
fruit flies were placed in 2 different jars one with fructose and one with Maltose and one with starch
Over many generations the flies adapted to their respective food sources
When the 2 different flies were placed in a mating cage, the flies preferred mating with others who shared the same adaptation (reproductive barrier was formed)
Sympatric speciation (same country)
speciation in populations that are not geographically separated (Same area)
Poly ploidy: animals or plants have an extra set of chromosomes due to error in mitosis ( common in plants)
Poly ploidy 4n causes reproductive isolation with diploid parents because 3n offspring has reduced fertility
Polyploid plant becomes reproductively isolated without geographic isolation and can form new species
Auto polyploid: animal or plant has extra sets and parents are the sae species
Allopolyploid: offspring has extra set of chromosomes but the parents are from different species (species close enough to produce hybrid)
Sexual selection: females mating choice (based on appearance) may eventually cause divergence ( their kids likely born with simlilar appearance and mating preference)
Habitat differenciation
A small group of main population exploits resource or habitat not used by the parent population
Ex apple maggot flies, the original fly used to be native to the hawthorn tree, and mated on their host plant
200 years ago a sub poulation of flies started colonizing on apple trees
colonization of apple trees lead to pre zygotic barriers (the 2 different flies dont interact
eventually the maturing of apples being fast promoted different mating seasons leading to temporal isolation
Ex apple maggot flies, the original fly used to be native to the hawthorn tree, and mated on their host plant
Hybrid zones and reproctive isolation
Hybrid zone patterns
On one side of the hybrid zone allele frequency is different from the other side
Allele frequency specific to the 2 parents species is close to 100% the farther it is away from hybrid zone
alleles frequency cannot change much past the hybrid zone because hybrid offspring poor survival and reproduction chance
typically placed in areas where the habitat of 2 different animals meet.
How Environment can effect on hybrid zones
cnages in environment alter where habitats on interbreeding species meet
black capped chickadees and Carolina chickadees hybrid zone has shifted northwards (due to change in climate)
series of warm winters caused a new hybrid zone between southern and nothern flying squirrels (previously their habitats did not overlap)
sometimes hybrid zone changes can can help parent species "cope" with changing enviromental conditions when hybrid between 2 species mates with parent species (extremely rare due o hybrid break down and viability issues)
Results of Hybrid zones over time
Reinforcement: reproductive isolation between 2 species is promoted because hybrids are either less fit than parents or sterile
Fusion: hybrids reproductive isolation between 2 species is reduced, so much geneflow can occur that the gene pools of 2 species can become more alike
Stability: hybrid individuals continue to reproduce whether it be because the are fitter than their parents (atleast in a certain habitat) or the parent species interact alot
how can rates of speciation be either fast or slow
Speciation rates
Rapid (punctuated)
fossils show that speciation can happen relatively rapidly
rapid changes in environment (mass extinction events can cause species to change rapidly relative to a more quiet period of time
Ex sunflowers: sunflower species made from hybridization, kick starts the speciation process
we see speciation happen rapidly (reflected by fossil record
gradual
states of relatively stable periods of earths life cycle lead to little to no change for millions of years
periods of punctuated equilibrium are seen in fossil record
study of speciation
study of speciation can reveal traits that cause reproductive isolation
as little as one single gene can reproductively isolate you from the rest of your species ( ex japanese snails of genus Euhadra)
speciation caused by something as small color on cichlids back can eventually lead to more pronounced differences eventually forming a group completely different form their ancestors
growth of one group of thriving organisms can shrink another group leading them to extinction. (these events helped shape and explain the changes in the fossil record
Fossil record patterns
punctuated equilibrium
species fossil records show long periods of slow evolution
suddenly after millions of years seemingly minimal evolution see species disappear and go extinct
missing fossil records
species with somewhat recent speciation (50000 years) dont show up in strata bacause sediment could not build in that short time
it appears that species did not evolve and suddenly went extinct