Lecture 9: Moving Onto Land Flashcards
How did the great oxygenation event help life move onto land?
It created oxygen which created ozone & the ozone layer to filter out UV radiation –> animals no longer needed to rely on water to filter out UV radiation.
How was desiccation a barrier to adapting to land?
Aquatic organisms adapted to being surrounded by water will dry out easily outside of water –> also cannot be completely waterproof since exchanges needed to occur –> smaller organisms dry out faster ( < surface area to volume ratio)
How was gas exchange a barrier to adapting to land?
CO2 and O2 are absorbed/released different depending on whether they are in air or dissolved in water –> need a new system of gas exchange
How was buoyancy a barrier to adapting to land?
water pressure supports body tissue but air does not –> land animals/plants need supporting structures.
How was temperature fluctuations a barrier to adapting to land?
temperature changes happen very slowly in the water (like 4˚C over the last few centuries) compared to on land where temps can change up to 30˚C in 24 hours
How was mineral nutrition a barrier to adapting to land?
water contains dissolved minerals (many aquatic animals are immobile and just take in the water around them for nutrients) but land animals would need a new way to supplement this.
How was reproduction a barrier to adapting to land?
aquatics organisms need water to facilitate reproduction –> male and female gametes release into the water for fertilization
How was vision and hearing a barrier to adapting to land?
light and sound waves travel differently through water and air –> need to adjust vision and hearing for this
What could have prompted plants to move onto land?
Plants are autotrophs and need sunlight to survive –> more advantageous to grow near the surface in shallow waters
How did organisms avoid desiccation issues?
Developed multiple cell layers and surface wax
evolved roots to directly move water into the water
How did organisms avoid gas exchange issues?
evolved specific pores to allow gases to enter
could be closed to prevent drying out
How did organisms avoid reproduction issues?
evolve spores which could survive desiccation ( and later seeds)
How did organisms avoid buyoancy issues?
evolved strong fibers and compounds (lignin and cellulose) for structural support
How did organisms avoid temperature fluctuation issues?
traits evolved to prevent desiccation eventually helped with this too –> plants evolved methods to survive extreme environments later (eg dormancy)
How did organisms avoid mineral nutrition issues?
roots allowed plants to take minerals out of the soil –> formed symbiotic associations with microbes/fungi to exchange minerals for sugars
Did plants or animals evolve onto land first?
Plants (animals came 30-100 MY after)
What was our first land ancestor?
Tikaalik –> lobe finned fish was the ancestor of all tetrapods
why could so many different animal groups colonize land?
structures that evolved for one use adapted to meet other challenges –> ex vertebrate skeletons provided structural support and allowed movement
How did animals adapt to avoid desiccation issues?
waxy coatings, scales, living in damp habitats, removing water from waste
How did animals adapt to avoid gas exchange issues?
developed small opening (trachea) to sacs filled with large surface area for gas exchange and to keep them from drying out
How did animals adapt to avoid reproduction issues?
developed internal fertilization –> fertilize inside the female and keep ova inside the body to prevent desiccation –> also maximizes the probability of gametes encountering one another
How did animals prevent desiccation of zygote/embryo?
modify egg for terrestrial life –> make an amniotic egg to be laid on land and incubate to maintain temperature
or
live birth: internal egg is retained after fertilization and increased parental investment in pregnancy increases survival of offspring
How did animals adapt to avoid buoyancy issues?
chitin exoskeleton, calcium shell or internal skeleton of cartilage/bone
How did animals adapt to avoid temperature fluctuation issues?
homeothermy –> the ability to regulate internal body temp either through metabolism (warm blooded) or behaviour (cold blooded)
Metabolic homeothermy has higher metabolic requirements and higher food requirements
How did animals adapt to avoid vision issues?
sealed chamber filled with fluid –> keeps eyes damp
How did animals adapt to avoid hearing issues?
cochlea in mammals still contains fluid for sound transmission
what is an anthropod?
an invertebrate with an exoskeleton (crabs, spiders, etc)
