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