Chapter 19: The History Of Life On Earth


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continental drift
 
the movement of continents in geological times; earth's crust and part of its upper mantle are divided into a series of plates that move laterally over the glove; by moving land-masses on and off the poles, continental drift has helped change the climate; has brought about the separation and mixing of living populations
source of life's raw materials: above, beyond or below hypotheses
 
methane, hydrogen, and ammonia provided by the atmosphere (above); outer space as the source of fully formed building blocks like amino acids, delivered by meteorites and comets- unlikely b/c it is unlikely that "seeding" could have brought a sufficient quantity of organic materials to get life going (beyond); from methane and hydrogen sulfide that gush out from deep-sea vents on the floors of the oceans- the very oldest organisms on Earth may have been heat-tolerant organisms, but scalding temperatures would have obliterated any early self-replicating molecules which were bound to be fragile- a much more likely home are sheltered stretches of ancient ocean beaches, where tides and shoreline rocks would have sorted organic materials and been joined by fresh materials delivered by ocean waves (below)
This single molecule performed both the DNA and enzyme roles, enabling the first living things to reproduce themselves
 
RNA
rybozymes
 
enzymes that are composed of RNA instead of protein; can encode information and act as enzymes; provide critical evidence of RNA's role in early life
Life is said to have begun when
 
RNA's precursor began to carry out variable self-replication; it is important that these molecules were able to vary from one another because only then could natural selection occur
The three domains of life are...
 
Bacteria, Archaea, and Eukarya
The four kingdoms within Eukarya are
 
Protista, Plantae, Animalia, and Fungi
Bacteria and archaea are made up strictly of...
 
single-celled microbes (are microscopic) and lack a nucleus (are prokaryotic)
protists
 
mostly microscopic and water-dwelling organisms; the term refers to many evolutionary lines
universal ancestor
 
the organism or group of organisms that gave rise to all current life
stomatolites
 
internal patterns found in rock deposits of Western Australia from 3.4 billion years ago that are so complex that it's likely they could only have been created by living organisms
Photosynthesis began in bacteria by at least 3.4 billion years ago, making available a massive quantity of energy-rich food
 

cyanobacteria were the first organisms to produce _______ as a by-product of photosynthesis
 
oxygen
Organisms that obtain their energy _________ can extract a great deal more energy from a given quantity than others that lack this capacity
 
aerobically; oxygen-aided
ancient bacteria that could metabolize oxygen took up residence in early eukaryotic cells and eventually struck up a ________ _________ relationship with them
 
mutually beneficial
Malnourished Earth Hypothesis
 
oxygen that built up in Earth's atmosphere 2.4 billion years ago weathered sulfur off the land and dumped it into the oceans, essentially creating a global toxic spill that effectively removed elements from the oceans that photosynthesizing eukaryotes (algae) needed to take up nutrients, resulting in a group of organisms so malnourished that they could not diversify very far through evolutionary processes
animals
 
multi-celled organisms that get their nutrition from other organisms or organic material
Cambrian Explosion
 
an alleged sudden appearance of the ancestors of modern animals beginning about 542 Mya
phylum
 
a group of organisms that share the same body plan; there are at least 36 phyla in the animal kingdom today; with one exception, every single one of these came into being in the Cambrian Explosion as indicated by the fossil record
modern animal phyla may have began to appear as much as a billion years ago, but large specimens of these phyla only appear in the fossil record beginning about 542 Mya
 
.
Even if the Cambrian Explosion was only an explosion of size, animals developed the capacity to eat one another, spurring animal evolution by bringing about the "arms race"
 
one animal's predatory adaptation spurs another's defensive adaptation and vice versa
The first multi-celled life on land were...
 
plant-fungi combinations (even today about 80%of plants have a symbiotic relationship with fungi, plants providing fungi with food through photosynthesis, fungi providing plant with water and mineral absorption through filament extensions); appeared sometime before 500 Mya
______ ______ gave rise to all of Earth's plants
 
green algae
one of plant's responses to the lack of water on land was to evolve a _________
 
cuticle, a waxy outer covering
one of plant's responses to gravity was to....
 
stay low, like mosses
plants have adapted to the land by developing a protective housing for embryos, which mature _______ a parent
 
within
byrophytes
 
represented by today's mosses, the most primitive land plants; lack vascular structure
vascular structure
 
a system of tubes that transports water and nutrients; plants without such a system have limited structural possibilities- they can grow out, but not up very far against gravity
seedless vascular plants
 
plants that have vascular structures (fluid transport) but don't reproduce using seeds; one of the four principal varieties of plantsex: ferns
seeds provide ______ and a ______ ______ _____ for an embryo
 
food; tough outer coat
gymnosperms
 
ex: pine and fir treesseeds are visible (pine-cones); represent the final liberation of plants from their aquatic past; there are about 7000 species today; travel by wind
angiosperms
 
flowering plants; evolved b/w 180 and 140 MYa, eventually succeeded gymnosperms as the most dominant plants on Earth, there are about 26,000 species today; use animals that travel from one angiosperm to another, picking up nectar and inadvertently delivering pollen, to reproduce
arthropods
 
first animals to move to land; their tough external skeleton (exoskeleton) prevents water loss and guards against the sun's rays
the movement of plants onto land made it possible for animals to follow
 
with plants came food and shelter from the sun's rays
gnathostomes
 
the family of fishes that are the ancestors of nearly all fish species today; were the first creatures to have jaws, which allow these vertebrates to grasp big chunks of food, offspring, and inanimate objects

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