ch 13 Flashcards
The earliest fossil cells closely resemble modern-day
bacteria.
Primitive cyanobacteria produced ___ and are thought to be ___.
the first oxygen in Earth’s atmosphere
the ancestors of chloroplasts.
Archaebacteria probably gave rise to the first
eukaryotes.
The evolution of multicellularity allowed for
“division of labor” among cells and allowed cell specialization that led to increased complexity in organisms.
All major groups of organisms alive today, except plants, originated some time during
the first hundred million years of multicellular life.
The have been five major mass extinction events on Earth. Human activity is contributing to what may become
a sixth mass extinction.
For the majority of the time that life has existed on Earth, organisms have lived only
in the water.
Not until the formation of an ozone layer that
blocks the sun’s ultraviolet radiation was it possible for living things to survive on land.
Ancient cyanobacteria
produced the oxygen that was converted to ozone.
Plants and fungi,
living symbiotically, were the first multicellular organisms to colonize the land.
The first animals to venture onto land were
the arthropods.
Vertebrates did not follow arthropods onto the land until
350 million years ago.
The first vertebrates were
small, jawless fishes.
Fishes with jaws appeared
around 430 million years ago.
The first terrestrial vertebrates evolved from
bony fishes.
The evolution of lungs, a more efficient circulatory system, and legs allowed amphibians to
move onto land for part of their lives.
A more complete solution to the problems of living on land is seen in the
reptiles, which evolved from amphibians.
Reptiles exhibit two key adaptations in vertebrate body design:
a watertight skin that prevents dehydration in the atmosphere
and a watertight, shelled egg that can be laid on land.
Birds and mammals, the dominant vertebrate groups on land today, evolved from
reptiles.
Earth is ___ years old.
4.5 billion years old.
The two trends in the way life has changed in the last 3.5 billion years…as time goes on…. life has gotten
more and more diverse (more species) and more complex.
First life forms were
bacteria (prokaryotes) - 3.5 billion years ago.
The first bacteria were
chemoautotrophs
chemoautotrophs
organism that got their energy from inorganic molecules like hydrogen sulfide. The complex mechanisms that could do photosynthesis did not evolve until much later.
3.4 billion years ago
Cyanobacteria – carry out photosynthesis, may be ancestors to chloroplasts.
When organisms first evolved to carry out photosynthesis there was a spurt of speciation - a whole lot of new species arose and a whole lot of life came about because:
now energy could be acquired everywhere (near the surface of the ancient seas) rather that the limited areas like underwater hot water volcanic vents, where the inorganic molecules could be found for chemoautotrophs to use. All these new areas and their differing environments (i.e. shallow warm tropical salt water versus deep warm tropical salt water versus shallow cold polar salt water…etc.) select for different traits in cyanobacteria and other bacteria that eat them or eat each other.
more TOTAL energy near the entire surface of waters (from the sun) can now power life (rather than small amounts of inorganic molecules found near underwater hot water volcanic vents)
Oxygen byproduct of photosynthesis important for life for two reasons:
Organisms that eventually evolve biochemical pathways to use oxygen in oxidative respiration get much more energy (ATP) per unit of food - more efficient in extracting energy. Again, there was a spurt of speciation, where a whole lot of new species arose and a whole lot of life came about because now these new and more energy efficient organisms could take jobs that were always there, but could not be taken by less-efficient organisms. 18 times more energy can be acquired from the same amount of food.
Later…. After the oceans become oxygen saturated oxygen gas O2 escapes into the lower atmosphere where it accumulates until it reaches the upper atmosphere where it is then converted to O3 (ozone) that will block harmful UV radiation… so that life could (eventually and much later) come on land. Again, there was a spurt of speciation, where a whole lot of new species arose because of new (land) resources/jobs available.
Eubacteria
most abundant and diverse kingdom today, some cause disease and some are decomposers.
Archaebacteria
cell membranes different (from Eubacteria) and produce protein from their DNA differently (from Eubacteria) in a process similar to Eukaryotes. Thought to be ancestors of first eukaryotes due to similar chemical processes such as protein synthesis. `
Several Eukaryotic organelles were probably
eubacteria species that got inside an arcahebacteria and continued to live and were passed down to daughter cells.
Because some Eukaryotic organelles (mitochondria and chloroplasts) have their own circular DNA and membranes similar to some Eubacteria, it is thought that
Eukaryotes arose when one archaebacteria engulfed, or was invaded by, a eubacteria and both continued to live and provide benefits to each other and when the archaebacteria divided, it’s hosted cell inside also divided and this endosymbiotic relationship was passed down.
Protists
first eukaryotes (1.5 billion years ago), mostly single celled. Some photosynthetic, some hunt bacteria or other protists. Greatest diversity among four eukaryotic kingdoms. Have membrane bound compartments called organelles which perform specialized functions. Again, there was a spurt of speciation, where a whole lot of new species arose and a whole lot of life came about because now these new and more complex and specialized organisms could take jobs that were always there, but could not be taken by less-more complex and less-specialized organisms
Six Kingdoms:
Eubacteria (prokaryote) - most diverse of all six
Archaebacteria (prokaryote)
Protists (eukaryote, mostly single celled) -most diverse of the 4 eukaryotic
Fungi (eukaryote, multicellular)
Plants (eukaryote, multicellular)
Animals (eukaryote, multicellular)
Sexual Reproduction
that evolved first in protists allowed for more genetic variation due to the more genetic shuffling (crossing over, independent assortment (flip flop) and parental gamete re-combination) which increased genetic variation and, therefore, the speed at which natural selection and evolution could take place and there was a spurt of speciation, where a whole lot of new species arose.
Multicellularity
allowed for division of labor and specialization of organisms cells and tissue.
Again, there was a spurt of speciation, where a whole lot of new species arose and a whole lot of life came about because now these new and more complex and specialized organisms could take jobs that were always there, but could not be taken by less-more complex and less-specialized organisms. They could also take the BIG jobs!
Multicellularity organisms evolved
independently many different times among protists.
Except for plants,
all major groups of eukaryotic organisms that survive today originated sometime during first 100 million years of multicellular life (Cambrian Period) – 600 million years ago.
Mass extinctions:
440 million years ago
360 million years ago
250 million years ago – 96% gone
215 million years ago
65 million years ago – 66% gone (dinosaurs)
After every major mass extinction
there was a spurt of speciation, where a whole lot of new species arose and a whole lot of life came about because now there were a lot of vacant jobs, that new species could occupy.
Symbiosis
beneficial partnership between organisms
Mycorrhizae
symbiotic partnership between plants and fungi which allows plants to survive on bare rock - enabled life to come on land.
relationship between plants and fungi
mycorrhizae
Fungi provides minerals to plant
Plant provides food to fungi
Only plants and their fungi parteners inhabit land the first 100 million years
Arthropods
first animals to populate land
hard exoskeleton and jointed appendages
Insects evolved from arthropods to become
most abundant group of animals.
Ability to fly enabled their success
to seek food, mates and nest sites
Some formed a symbiotic relationship with some flowering plants that greatly benefited both:
Insect pollinators got food (nectar) from plants and plants had male gametes (pollen) delivered door-to-door to female gametes making sexual reproduction much more efficient and prolific
First vertebrates were
jawless fishes – 550 million years ago.
Then after the first vertebrates
Jawed armored fish….sharks and boney fish…..amphibians….reptiles….dinosaurs and mammals…birds
350 million years ago
amphibians are the first vertebrates to inhabit land
The 2 events OFTEN lead to rapid speciation:
Extinction - because many jobs vacated by species that became extinct are now available.
A radically new type of life form or feature - enables organisms with the feature to take jobs that were always there but could never have been taken before
life first appeared
(3.5 billion years ago)
first photosynthesis
(3.4 billion years ago)
the appearance of the first eukaryotes
(1.5 billion years ago)
sexual reproduction
(1.2 billion)
first multicellular organisms
(630 million years ago)
Cambrian explosion
(600 million years ago)
first life forms to invade land
plants and fungi (430 million years ago)
first animals to invade land
arthropods (380 million years ago)
