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Honors Environmental Science Week 17 pt 3
Terms in this set (27)
Eukaryotic cells have
have a nucleus
All complex cells and nearly all multicellular animals are
how did eukaryotes evolve from prokaryotes?
small prokaryotic cells live together in symbotic relationship. Small cell types took on specialized function and became the organelles within a larger cell
what is a symbiotic relationship
different types of small cells were beneficial to each other and none harmed the others
any of a number of organized or specialized structures within a living cell.
how did organelles help the evolution of prokaryote to eukaryote?
organelles supplied nrg, broke down wastes, did other jobs needed for cells to become more complex
how old is the thought to be oldest eukaryote fossil
2.1 billion yrs
Why did eu become more dominant?
eukaryotic cells were much better able to live and replicate themselves, continued to evolve and become dominant life form over prokaryotic cells
prokaryotes and eukaryote can both be...
the first multicellular organisms were probably..
prokaryotic and cyanobacteria
Multicellulairy may have evolved how many times?
more than once in Earth's history, like at least once for planet and once for animals
why are there so few fossils of early multicellular organisms?
because they were soft bodied and did not fossilize well
when did the explosion in the number and type of life forms occur?
at the beginning of the Cambrian
What was life like at the end of the precambrian?
it was coming more complex. Found evidence of diverse multicellular organisms.
found toward END OF PRECAMBRIAN Have a variety of forms of symmetry - from soft to rigid, take form of disc or bags or quilted mattresses
when does it look like the edia cara appear?
as earth defrosted from a world wide glaciation
Why di it take 4 bill years for organisms as complex as the ediacara biota to evolve. Some explanations
1. evolutionary processes are long
2. takes long time for complexity to evolve
3. atmospheric oxyfen was limited, so complex organisms could not evolve
4. planet too cold for complex live
5. complex life evolved was wiped out by massive global glaciations
why did the ediacara organisms die out, if they did?
1. evolution of predators w/ skeletons in cambrian
2. competition from more advanced cambrian organisms
3. changes in environmetal conditions caused by super continent breakups
What sorts of changes in environmentlal conditions because of the breakup of a super continent?
rising sea level, limited nutrients, changing atmoospheric and oceanic chemistry
the existence of ediacaran fauna shows...
that a diversity of life forms existed before the cambrian
what are adaptations?
the characteristics of an organisms that help it to survivee in a given environment
Adaptations are traits that an organisms inherits from?
Within a population of organisms are genes...
and these gens code for a certain number of traits
How do adaptations develop
when certain variations help some members survive better than others. Variation may already exist in population
differences in a population
random change in organisms genes. some are harmful and organism dies - and that variation will not remain in population.
What happens to Neutral mutations
remain in population. If environment changes, the mutation may be beneficial and may help the organisms adapt to the environment. the organisms pass this favorable trait to their offs bring