Origins Of Life And The Cambrian Explosion

Question 0

Single common ancestor?

Answer 0

Yes - shared characteristics (cells, DNA, proteins, ribosomes for forte in synthesis (except viruses), genetic code, L isomers of same 20 amino acids)

Question 1

Age of earth and oldest rocks

Answer 1

Earth - 4.6 bya
Oldest rocks - 3.6-3.8 bya
Subduction or plate tectonic movement makes it hard to know when life originated

Question 2

Life originated multiple times?

Answer 2

Possible, don’t have enough evidence of this

Question 3

Life

Answer 3

Self-replicating (store and transmit information - genotype, express that information - phenotype), evolving (heritable changes in genotype, selection acts on phenotype)

Question 4

Organic molecules

Answer 4

Molecules made up of carbon with other attached elements

Question 5

Origin of first organic molecules

Answer 5

1. Produced from inorganic molecules in earths early atmosphere
2. Arrived in meteorites

Question 6

Transition from non-life to first self-replicating life form

Answer 6

1. Origin of organic molecules (1st amino acids and nucleotides)
2. Polymerization of organic molecules (1st proteins and nucleic acids)
3. Self-replication of polymers

Question 7

Montmorillmite

Answer 7

Natural clay to which organic materials stick, nucleotides and amino acids polymerize when stuck, step 2 of creating life, 8-10 nucleotides polymerize, with primer >50 can polymerize, create hypothesis for origin of nucleotide polymers

Question 8

Polymers

Answer 8

Bundle of nucleotides

Question 9

Ribozymes

Answer 9

RNA enzymes, form and break phosphoester bonds, important reactions for replications nucleic acids, can possess both phenotype and genotype

Question 10

RNA world hypothesis

Answer 10

Catalytic RNA molecules were the transitional form between non living matter and the earliest cells

Question 11

Transitional from from non living from to early cells

Answer 11

DNA: can’t create phenotype itself (can’t do biological work) so no
Proteins: can’t store or transmit info to next generation so no
RNA: possesses genotype and phenotype because of ribozymes, important in protein synthesis, can replicate in lab experiments

Question 12

Ribozymes and self-replicating

Answer 12

Known RNA molecules can’t completely self-replicant without proteins but RNA can replicate in labs

Question 13

Traditional classification

Answer 13

Old 5 kingdoms are Monera, fungi, plants, animals, and Protista, phylogenetic analysis based on ribosomal RNA change grouping, Monera not monophyletic, Protista not monophyletic, plant, animals and fungi are still good monophyletic groups

Question 14

3 new domains

Answer 14

Bacteria, Archaea, Eukarya

Question 15

Explosion of animal life forms

Answer 15

540 million years ago

Question 16

Precambrian

Answer 16

Before the Cambrian explosion

Question 17

Cambrian

Answer 17

The Cambrian explosion and onward (~495-543 mya), period in Phanerozoic eon right before/during the Paleozoic era

Question 18

Cambrian explosion

Answer 18

Almost all animal phyla appeared in the span of about 40 million years all over the world, explosion of morphology not lineages

Question 19

Radial symmetry

Answer 19

Symmetry in more than one direction, can divide in multiple planes

Question 20

Bilateral symmetry

Answer 20

One division down the middle and looks the same on each side

Question 21

Precambrian fauna

Answer 21

Ediacaran fossils (565-544 mya) in Australia: small (few cm) sponges, jellyfish, comb jellies, radial symmetry or lacking symmetry, little or no bilateral symmetry (no mollusks, worms etc)

Question 22

Cambrian fauna

Answer 22

Burgess Shale (520-515 mya) in British Columbia: explosion of body plans, tissue types, developmental plans, lots of bilateral symmetry, segmentation, heads and appendages

Question 23

Precambrian and Cambrian fossil record

Answer 23

Supports the time span and rapid change in species and diversity, bilateral groups appear later

Question 24

Precambrian and Cambrian molecular genetics

Answer 24

Supports span of time and increased diversity, bilateral species came later

Question 25

Explosion of body types

Answer 25

1. Photosynthesis by Proterozoic algae increased the o2 (allowed for larger body size hence evolution if tissues and allowed for higher metabolic rate hence more movement)
2. Mass extinction event of earlier fauna (may have created opportunity for new lineages to diversify)