Moving onto Land Flashcards
eras leading up to the emergence of life on land
- proterozoic
- cambrian
proterozoic era
- eukaryotes evolved, acquired photosynthesis
- proliferation of bacterial mats
- animals: soft bodied, sessile or slow-moving
- at the end: multicellular photosynthesizers began to appear (algae)
great oxygenation event
-cyanobacteria released oxygen as a waste product
- oxygen was initially fixed in dissolved iron or organic matter
- (aka oxygen sinks)
-after 200MY, sinks were saturated and O2 began building up in the atmosphere
- led to massive die-off of other bacterial species
- also formed Ozone Layer
cambrian era
- shells and other “hard bodies” start to dominate
- animals become more motile
- explosion of evolution of new body types in animals
early ordovician era
- bacterial mats seen in the Proterozoic were greatly reduced
- evolution of developed complex multicellular forms
- acquired the ability to respire with oxygen
- all life still in the ocean
ordovician
early plants energy on lans
-first plants are very small, they do not produce flowers or seeds
devonian
- the first animals leave the water (arthropods)
- vertebrates emerge shortly after
- animal life largely vulnerable to desiccation, still dependent on water for reproduction
the carboniferous
- broke dependence on water for reproduction
- proliferation of forests
- carboniferous coal swamps
barriers to adapting to land
- desiccation
- gas exchange
- reproduction
- buoyancy
- temperature fluctuations
- visual and hearing
- mineral nutrition
- harmful ultraviolet radiation
desiccation
- drying out
- animals used to be surrounded by water, smaller you are the faster you dry out, no animals are water proof because they need gases and water to flow through body
gas exchange
CO2 and O2 absorbed differently depending on if you are on land or water»_space; gills vs lungs, plants and animals have different chambers that allow respiration to occur
reproduction
most animals were releasing gametes into water, nothing on land could help move egg and sperm to meet
buoyancy
water and water pressure would support body tissues, air would not, provided structural support for life
temperature fluctuations
seawater = slow and little change , land = quick and large changes
vision and hearing
light and sound waves move differently through water compared to air
needed to adjust vision and hearing
mineral nutrition
-water contains dissolved minerals for added nutrition
need to find a way to supplement nutrition lost, many species were sessile in water (fixed), no terrestrial species»_space; only plants who capture energy from sun could afford to be sessile
harmful UV radiation
water = filter uv light, gases = poor filter, for most of eath’s history life could not withstand light on surface
Great oxygenation = created ozone shield
First life on Land
-plants
Since autotrophs, all about getting most sun, which meant they would grow as near to surface as possible
First Photosynthesizers: appeared 3.4 billion years ago
Cyanobacteria = first to use chlorophyll , anything that uses photosynthesis evolved from this cell
evolution of green algae
- concentrated in shallow water
- exposed to periods of drought
- evolved into forms that could survive on land: liverworts and mosses
liverworts and mosses
- no roots
- no seeds
- no flowers
- very small
- no distinct leaves or stems
- no vascular system
plants and animals in the late Devonian
- ferns, horsetails
- arthropods
- Vertebrates and Amphibians
why could so many groups colonize land?
many animals preadapted to life on land
-structures that evolved for other uses are also effective for living on land
what was the motivation to go to land?
predation, land as protection,
as plants made it to land»_space; want to eat the plant have to go to land,
