History Of Life

Question 1

Macroevolution

Answer 1

occurs over large - scale time
Origin of key biochemical processes
Emergence of the first terrestrial vertebrates

Question 2

How did life originate?

Answer 2

Biochemical and physical processes on early earth, aided by natural selection gave rise to small simple cells
4 step process

Question 3

The abiotic synthesis of small organic molecules

Answer 3

Organic molecules are being synthesized by abiotic sources
Miiler - Urey (1953) university of Chicago
Using means, ammonia, hydrogen, and water with lightning as an energy source
were able to incorporate carbon into organic compounds
Depended on lightning
Required a source of electrons
Juan Oro (1961) -
showed that amino acids could be made from hydrogen cyanide and ammonia in an aqueous solution
Large volume of adenine
Both experiments relied on reduction
Required a reducing atmosphere to make molecules
Small pockets of atmosphere around volcanoes and deep sea vents that were reducing
Meteorite - chondrites - 1-2% of their composition is carbon, supports existence of amino acids outside biological systems

Question 4

From small molecules to macromolecules

Answer 4

Macromolecule: single or identical monomers
Amino acids and RNA nucleotides when dripped onto a substrate (sand, clay, or rock) spontaneously form polymers
Polymer of amino acids - polypeptide
Polymer of RNA nucleotide - polynucleotide
May be precursors of modern day proteins of RNA

Question 5

Protocells

Answer 5

Life requires reproduction and metabolism
Self-replication molecules
Metabolism-like source of small molecules
Appeared together as protocells
Protocells will form spontaneously from organic macromolecules
Liposomes: type of vesicle that form when lipids are added to water
Montmoorilonite (soft mineral clay)
Increases rate at which vesicles form
Vesicles can reproduce and can carry out basic metabolic reactions
If they absorb RNA and other organic molecules

Question 6

Origin of self-replicating molecules

Answer 6

RNA can carry out a # of enzymatic functions
RNA catalysts = ribozymes - complementary copies of small pieces of RNA - nucleotides available
Natural Selection can act on pieces of RNA
RNA with a particular nucleotide sequence may be:
1. more stable
2. Can replicate faster with fewer errors
More descendants that contain RNA molecules will be produced
Continued replication - mutations and errors can occur - differences in nucleotide sequence - more stable molecule
RNA - DNA
DNA is more stable than RNA - because of its double helix

Question 7

Fossil Records

Answer 7

Document the history of life
Show changes in types of organisms that dominated life on earth
Sow that organisms of the past are quite different than today’s organisms
Show that organisms that were once common are now extinct
Show how new organisms arose from pre-existing organisms
Incomplete: doesn’t show all evolutionary change
1. Many organisms are not fossilized or preserved
2. Fossils have been destroyed due to geological processes (earthquakes/volcanic eruptions)
3. Fossils not found yet

Question 8

Dating of fossil and rock

Answer 8

Soil sediments are layer down over time
Some organisms are fossilized and sediments are turned to rock
Can look at rock layers and determine relative age of fossils
Sequence does not tell actual/absolute age - radio metric dating - based on decay of radioactive isotopes
Parent isotopes: decay to daughter isotopes at a constant rate
Rate of decay is measured in half - lives - amount of time for 50% of the parental isotope to decay
Accumulating isotopes
Carbon 14 decays & carbon 12 doesn’t
To date fossils:
Use ratio of C 14 + C 12
Old fossils:
1. Have isotopes with short half - lives — none to measure
2. Fossils are found in sedimentary rock - can be difficult to use indirect method of dating
Indirect method of dating - use isotopes to date volcanic rock layers

Question 9

Origins of new groups of organisms

Answer 9

Fossils show how new features arose and how long it took
Mammals gradually evolved from a group of tetrapods called synapsids
Over time mammals evolved a lower jaw consisting of one bone
Single hinge between upper and lower jaw
Differentiated teeth

Question 10

Key events in earths history

Answer 10

3 major events:

1. Origin of single - celled prokaryotes
2. Development of multi-cellular organisms
3. Origin of life on land

Question 11

Prokaryotes

Answer 11

Stromatolites - certain prokaryotes link thin filaments of sediments together
3.5 billion years ago

Question 12

Photosynthesis

Answer 12

Photosynthesis: aquatic bacteria - Cyanobacteria - 2.7 billion years ago
Oxygen dissolved in water produces iron oxides - increase
- gassed out into atmosphere- oxygen increased for 0.5 billion years
Rapid increase in oxygen in atmosphere due to evolution of eukaryotic cells that contain chloroplasts

Question 13

Eukaryotes

Answer 13

Evidence supports serial endosymbiosis
Mitochondria and plastids (chloroplasts) were small prokaryotes that injured larger prokaryotes
Entered as:
1. Bits of in digested prey
2. Parasites
All eukaryotes contain mitochondria and only some contain chloroplasts
Mitochondria evolved before chloroplasts

Question 14

The origin of multicellularity

Answer 14

Fossils and DNA sequencing
Common ancestor to multicellular eukaryotes lived 1.2m to 1.5 billion years ago
Larger more diverse eukaryotes do not appear until 565 million years ago
Geological evidence: series of ice ages - limited life
1. Deep sea vents & hot springs
2. Limited to open ocean water which was only found around equator.
30 million years

Question 15

Cambrian explosion

Answer 15

Cambrian explosion
Origin of many phyla of current living animals
Prior to explosion:
1. Animals had soft bodies
2. Herbivores, filter feeders, scavengers
Cambrian explosion
1. Predators
2. Prey - defensive adaptations - sharp spikes & body armor

Question 16

Colonization of land

Answer 16

2 adaptations: 
1. Reproduce on land
2. Prevent dehydration
Plants & fungi - 420 million years ago
Earliest tetrapods (animals) - appeared 365 million years ago on land

Question 17

Continental Drift

Answer 17

Continents are part of the plates
1. When the plates move it is part of continental drift
2. Alters the habitat for organisms
Some moves toward the North Pole and some move toward the South Pole
3. Organisms have 3 choices
1. Evolve
2. Move to different location
3. Go extinct
4. Results in geographic isolation
- allocative speciation
5. Explains while fossils of the same species are found in locations that are far apart
6. Explains current distribution of species

Question 18

Permian mass extinction

Answer 18

occurred about 215 million years ago. Resulted in loss of 96% of ocean life and a large # of insects due to extreme volcanic activity — get lava, ash, and an increase in carbon dioxide concentrations which warmed the planet — little differences in temps at the pole and at the equator — decrease mixing of ocean water — decrease in oxygen concentration in the water and organisms die

Question 19

Cretaceous mass extinction

Answer 19

65.5 million years ago. 50% marine species lost. Lost large # of groups of terrestrial plants and animals – dinosaurs. Cause is uncertain, however is hypothesized that it is due to a meteorite, asteroid, or comet — cloud of hot vapor and debris that kills the animals and plants

Question 20

Consequences of mass extinction

Answer 20

5 - 10 million years for diversity levels to reach previous levels prior to extinction (mass). Alters ethnological communities.
After extinction - increase % marine predators.
Loss of complete lineages of organisms- with advantageous features.
Did become extinct with a mass extinction
Can also lead to adaptive radiation
Loss of some species might result in the dominance of other species, these species evolve and form new species

Question 21

Worldwide adaptive radiation

Answer 21

Adaptive Radiation: did occur after each 5 extinction
1. Survivors adapt to vacant ecological niches or roles
-ex: early mammals limited in size and diversity. Because they were eaten or outcompeted for resources by the dinosaurs. When dinosaurs went extinct, mammals increased in size and diversity.
Can shape the overall history of life :
1. Responsible for origin of photosynthetic prokaryotes
2. Predators during Cambrian explosion
3. Adaptive radiation followed colonization of land by plants, insects and tetrapods

Question 22

Heterochrony

Answer 22

change in rate and timing of developmental events
Organisms shape is affected by the relative growth rates of body parts
Can also alter the timing of reproductive development relative to the development of non-reproductive organs
Results in adults that retain body features that were juvenile structures in the ancestral species = paedomorphism

Question 23

Changes in spatial pattern

Answer 23

Can result from alterations in genes that control the placement or special arrangement of body parts
Master regulatory genes called homeotic genes determine basic features of the organism
Evolution of vertebrates from invertebrates
2 duplications of homeotic genes that have been identified in every vertebrate genome. Not present in invertebrates

Question 24

Evolution of development

Answer 24

Of new & existing genes - developmental genes
Gene duplication events - new developmental genes - facilitates evolution of organisms with new structures or arrangements of different structures

Question 25

Changes in genes

Answer 25

Identified changes of developmental genes at are associated with the rise of the 6-legged insect from an ancestor with many more legs - ancestor is the artemia
Found a specific developmental gene (ubx) - suppresses limb development in insect - 0 in artemia
The exact amino acid changes that result in reduced limb formation in the insect have been identified

Question 26

Changes in gene regulation

Answer 26

Changes in the regulation of the expression of a gene- can occur in a single cell type
Regulation of expression of gene is in the non-protein coding portions of the DNA
Stickleback fish: found in the ocean and lakes of western Canada
Ocean- have ventral/abdominal spines
Canada- no ventral spines
Change in regulation of expression of pitx1 gene