History of Life On Earth

Question 1

How long ago did the Earth form?

Answer 1

4.6 billion years ago

Question 2

what did earths early atmosphere consist of and not consist of?

Answer 2

-lots of water vapor due to volcanic eruption
-methane, nitrogen, ammonia, and some CO2
-no oxygen

Question 3

what 4 big stages were responsible for life forming on earth?

Answer 3

-abiotic synthesis
-synthesis of polymers
-packaging into protocells
-origin of self replicating molecules

Question 4

what is abiotic synthesis?

Answer 4

-the accumulation of organic monomers: raw materials forming amino acids as well as sugars, lipids, nucleic acids

Question 5

what is synthesis of polymers?

Answer 5

-abiotic synthesis of RNA can spontaneously occur from precursor molecules
-polymers can be formed through dripping amino acids and RNA onto hot rock

Question 6

what are protocells?

Answer 6

-early cells: self replicating molecules with early enzymes & vesicles

Question 7

what is the origin of self replication?

Answer 7

-RNA - carries out enzyme like activities
-can catalyze own reproduction with ribosomes, likely meaning world was RNA filled at first before DNA

Question 8

what are the 3 main methods of documenting early life?

Answer 8

1. sedimentary strata: used to determine age of fossils based on order in stratum
2. index fossils: similar fossils found @ same strata in different locations
3. radiometric dating: using 1/2 life of isotopes to determine age of fossils

Question 9

when were the oldest fossils found and what kind of fossil were they?

Answer 9

-3.8 billion years ago: oldest fossils in the form of prokaryotic cells: anaerobic, heterotrophic (cannot produce own food)

Question 10

when were the first cyanobacteria found and what did they do?

Answer 10

-3.5 billion years ago
-underwent photosynthesis, meaning O2 produced could react with iron to form iron oxide, rusting rocks

Question 11

how did o2 become prevalent in the atmosphere?

Answer 11

-o2 dissolved in water, reacted with dissolved iron
-iron became iron oxide, accumulated in sediment
-eventually, o2 accumulated to the point where it became saturated and “gassed out” entering the atmosphere

Question 12

when did oxygen accumulate in the atmosphere and when did the first eukaryotic cells show up?

Answer 12

2.7 bya - oxygen accumulates
2.1 bya - eukaryotes found

Question 13

what is the endosymbiotic hypothesis?

Answer 13

-a theory that eukaryotic cells came into existence by including chloroplasts & mitochondria into their cytoplasm [AKA - saying that these are both bacterial organisms that are not “our own”

Question 14

when did multicellular eukaryotes and organisms begin to show up?

Answer 14

1.2 bya - oldest fossils of multicellular eukaryotes
1.0 bya - 700 mya: complex multicellular organisms begin to show up

Question 15

what was the cambrian explosion and when did it occur?

Answer 15

-cambrian explosion refers to an event that formed most of the major phyla: sponges, arthropods, molluscs, etc
-occurred 540-520 mya

Question 16

when did land get colonized by fungi, plants, and animals?

Answer 16

500 mya

Question 17

what is the snowball earth hypothesis?

Answer 17

-a hypothesis that 750-550 mya, the earth was covered in ice/snow

Question 18

what 3 large scale processes influence organism development?

Answer 18

-tectonic plate shift
-mass extinctions
-adaptive radiation

Question 19

what are plate tectonics / continental drift?

Answer 19

-PT = plates of rock under earth that push or pull against each other
-CD = earth began as pangaea 250mya, separated into modern day arrangement 250-60 mya

Question 20

what are the two major mass extinctions? what caused them?

Answer 20

1. permian = likely volcanic eruptions, lost 96% of marine animals and 8/27 insect orders
2. cretaceous = large meteor hit earth, killing the dinosaurs!!

Question 21

what is adaptive radiation?

Answer 21

-the evolution of a diverse range of adapted species from one common ancestor, results in increased diversity
-may follow mass extinctions or the colonialization of new regions

Question 22

what is evo-devo?

Answer 22

evolutionary biology & development: research of these two mechanisms to look at fossil records and examine genetic change

Question 23

what is evolution of development?

Answer 23

-rate of development of body parts &
-allometric growth = positioning of body parts [ex - skull shape]
-heterochrony = change in timing or rate of development

Question 24

what is paedomorphosis?

Answer 24

-retention of juvenile structures in adult form, showing features found in ancestral juveniles
ex - gills in adult salamanders

Question 25

what are homeotic genes?

Answer 25

-genes that determine basic features: where wings on a bird will develop and how they will develop, or how a flower’s parts are arranged

Question 26

what are hox genes?

Answer 26

-a subset of homeotic genes that provide positional information for fins in fish and limbs in tetrapods
hox6 = controls limbless regions