Lecture 23, 24- Origin of Life; Cambrian Explosion

Question 1

What is life?

Answer 1

1. ) Capable of reproduction
2. ) Able to metabolize
3. ) Contain phenotype and genotype
4. ) Able to evolve

Question 2

Life on earth evolved: ___ years ago

Answer 2

3.8 billion (or 3,800 mya)

Question 3

Prokaryotes evolved: ___ years ago

Answer 3

3.5 billion (or 3500 mya)

Question 4

Eukaryotes evolved: ____ years ago

Answer 4

2.1 billion (or 2100 mya)

Question 5

Multicellular eukaryotes evolved about: ____ years ago

Answer 5

1.5 billion (or 1500 mya)

Question 6

Average size of fossils increased from __ microns to ____ microns

Answer 6

10 microns; 60-80 microns

Question 7

When was the earliest possible euk dated?

Answer 7

~1.8 bya in Canadian shield region

Question 8

Serial Endosymbiotic Hypothesis

Answer 8

all mitochondria are monophyletic; chloroplasts have evolved several times –> Polyphyletic

Question 9

Biases in Fossil Record

Answer 9

1. ) Geographic
2. ) Taxonomic
3. ) Temporal

Question 10

When was the Cambrian Explosion?

Answer 10

about 540 million years ago

Question 11

What was the Cambrian Explosion?

Answer 11

appearance of complex metazoans; appearance of protostomes and deuterostomes, coelomates, pseudocoelomatse and acoelomates; 1st segmented body plans, external skeletons, appendages, and notochords

Question 12

Causes of Explosion

Answer 12

1. ) increase in oxygen content in seawater
2. ) Origin of Hard Parts
3. ) Evolution of Eyes
4. ) Genetic Changes

Question 13

How did genetic changes affect the Cambrian Explosion?

Answer 13

diversification of homeotic genes; activated suites of genes that control body plans during early development

Question 14

What do homeotic genes encode?

Answer 14

Homeotic genes encode for transcription factors

Question 15

What are the Macroevolutionary Patterns?

Answer 15

1. ) Adaptive Radiation
2. ) Punctuated Equilibrium
3. ) Mass Extinctions

Question 16

Adaptive Radiation

Answer 16

evolutionary divergence of members of a single phyletic line into a series of rather different niches or adaptive zones

Question 17

Generalizations of Adaptive Radiation

Answer 17

1. ) occur at edges of a species range
2. ) facilitated by absence of competitors and predators
3. ) may involve “general adaptations”

Question 18

Punctuated Equilibrium (PE)

Answer 18

• 1st proposed by Stephan Jay Gould and Niles

- account for “gaps” in fossil records

Question 19

2 Characteristics of Punctuated Equilibrium (PE)

Answer 19

1. ) periods of rapid morphological change co-occur with periods of rapid selection
2. ) after species formed–> exhibit “stasis”

Question 20

Mass extinction

Answer 20

identified when extinction on rates well above normal “background extinction”

Question 21

The end-Permian mass extinction occurred approximately:

Answer 21

250 million years ago

Question 22

The end-Ordovician mass extinction occurred approximately:

Answer 22

439 million years ago

Question 23

The Late Devonian mass extinction occurred about:

Answer 23

367 million years ago

Question 24

The end-Triassic mass extinction occurred about:

Answer 24

215 million years ago

Question 25

The Cretaceous-Tertiary (K-T) mass extinction occurred about:

Answer 25

65 million years ago

Question 26

The discovery of undescribed amino acids in meteorites provides support for which step of the chemical theory of the origin of life?

Answer 26

Inorganic molecules –> organic molecules