history of life

Question 1

bubble hypothesis : how complex polymers evolve

Answer 1

• waves drive bubbles onto the shore
• oily (with phospho-lipids) bubbles last longer
• primative ‘membrane’ enclosing nucleotides and exposing them to UV
• organic polymers form in the protected bubbles
• some would be better ay replicating insdie the bubbles than others

( decomposing seaweed released phospholipid in the sea )

Question 2

clay hypothesis: how complex polymers evolve

Answer 2

• clay is made of silicate crystals in solution
• cyrstals form up in a regular structure and spontaneously ‘replicate’
• organic monomers attracted to silicate cyrstals
• different patterns of silicate under ‘ selection pressure ‘
• replicating organic molecules are an exaptation
• eventually become independent of clay scaffold

Question 3

exaptation

Answer 3

the process by which features acquire functions for which they were not originally adapted or selected

Question 4

extra-terrestrial hypothesis 1 : comets

Answer 4

‘exogenesis’

• in space organic compounds are quite common
• in out solar systems volitiles ( evap. on earth ) dont evapourate as little heat from sun
• comets often encrusted with ‘tar’ like substance
• could have rained down on earth
• introduction of complex polymers

Question 5

extra-terrestrial hypothesis 2 : mars

Answer 5

• life apperared on earth very soon after its formation
• little time for the crust to cool down
• mars is smaller than earth so it called faster and life formed here first
• bits of mars blasted off by asteroids impact and arrived on earth
• introduction of complex molecules

Question 6

the first cells

Answer 6

( hydrothermal vents - molecules trapped in porus edge )

• replication more efficent when catalysed by enzymes
• selection would favour molecules that concentrate enzymes
• enclosure in a membrane
• phospholipids spontaneously from enclosed membranes

Question 7

’ stromatolites ‘

Answer 7

layered sedimentary formations that are created mainly by photosynthetic microorganisms such as cyanobacteria

fossil evidence for living cells
- fossilised cyanobacteria, 3.5-2 bya

Question 8

the first eukarya

Answer 8

large cells, nucleus, organelles, divide by mitosis

fossilised eukaryotic cells 2.2 - 1.8 bya

Question 9

origin of eukarya

Answer 9

• eukarya evolved by symbiosis between archaea and bacteria
• an archeon engulfs a bacterial cell, which evolved into mitochondria
• mitochondrial genes closer to bacterial genes than nuclear DNA

Question 10

multi - cellular life

Answer 10

• more than one type of cell - differentation
• some form of develpment
• a single zygote to an adult with multiple cell types
• mostly eukaryotes
• molecular clock suggest development evolved 1.5 bya
• first multicellular algae fossils 1.2 bya

Question 11

Opisthokonts

Answer 11

large group of eukaryotes - animal and fungi kindom

(unifying feature of opisthokonts is the presence of a flagellum)

flagellate cells ( sperm or zoospores ) propelled by a single prosterior flagellum

animals ( Metazoans ) : lack ridgid cell walls, multi-cellular, tissues develop from embyonic layers

Question 12

Metazoa - multicellular animals

Answer 12

not in fossil record until 0.7 to 0.55 bya

ediacarian fauan :

• Cnidarians ( > 9000 species - mainly marine animals )
• Worms

Question 13

ediacaran fauna

Answer 13

unique assemblage of soft-bodied organisms preserved worldwide as fossil impressions in sandstone from the Ediacaran Period

Question 14

the origin of animals

Answer 14

1. colony of flagellate protist ( more advantagous than own - more falgellum = more speed )
2. more advantageous if form hollow sphere flagellum facing out - large SA
3. more advantageous when so big not all cells need to make flagella can become specialised cells ( e.g. somatic cells , reproductive cells - reproduce more efficiently )
4. cells that dont need to intract with the environment - make sence keep protected . protect with little dimple - which also acts as digestive cavity

Question 15

metazoan phyla

Answer 15

• most metazoan phyla appear suddenly (in fossil record) between 500-540 mya

molecular evidence - suggests metazoan phyla emerged much earlier than 1200 mya. ( no hard skeletons )

Question 16

animal phylogeny : morphological hypothesis

Answer 16

morphology during development (embryonic morphology)

based on what they looklike

Question 17

phylogeny

Answer 17

the history of the evolution of a species or group, especially in reference to lines of descent and relationships among broad groups of organisms.

Question 18

morphology

Answer 18

a branch of biology that deals with the form and structure of animals and plants

Question 19

animal phylogeny : molecular hypothesis

Answer 19

using molecular methods splitting into groups

Question 20

Chordata (phylum)

Answer 20

(human phylum)
defining features: 
- dorsal, hollow nerve cord
- pharyngeal slits (openeing between throat and outside) 
- notochord
- postanal tail

Question 21

Cephalochordata ( lancelets )

Answer 21

( subphylum - chordata )

fishlike marine invertebrates

• pharyngeal gill slits
• notochord retained into adulthood

Question 22

Tunicats

Answer 22

( subphylum - chordata )

marine invertebrate animal

Question 23

vertebrates

Answer 23

( subphylum - chordata )

chordates with a back bone

in adults function of notochord has been taken over by flexible back bon - selective advntageous

0.04% of animal species