What are the "big three" things biologists think an organism needs to be considered alive?
- 1. Energy transformation - transform energy to synthesize new molecules
- 2. Reproduce - make nearly faithful copies of themselves
- 3. Maintain homeostasis - regulate internal environment in response to external changes
What sources of energy are used by life?
- 1. light
- 2. inorganic compounds (H2, H2S etc.)
- 3. organic compounds (starch, fats etc.)
- can make organic molecules usig inorganic compounds and outside energy
use light energy and CO2 to make glucose
use chemical energy and CO2 to make glucose
- consume organic molecules as both energy source and carbon source to transform into other organic molecules
- examples: animals and fungi and many bacteria
- Use light as energy source but obtain carbon from food
- example: certain bacteria
What is asexual reproduction?
- "without sex"
- no union of gametes
- little to no genetic difference
What is sexual reproduction?
- union of gametes
- genetic difference between parents and offspring
What is the definition of evolution?
genetic and resulting phenotpic change (observable property) in populations of organisms from one generation to the next
What are some examples of "living fossils"?
- ginkgo biloba
- horseshoe crab
How is genetic analyses revolutionizing our understanding of Neanderthals?
- DNA analyses indicate that Neanderthals and Humans interbred
- DNA extracted from leg bones, now 60% of Neanderthal genome has been sequenced
- Found Neanderthal DNA fragments are scattered through genome of non-African ancestry
What is the importance of the Miller and Urey experiments (1950s)?
- 1. mimic earth's early atmosphere (CH4, N2, NH3, H2, H2O, CO2)
- 2. zap with electricity
- 3. condense and analyze for simple organic compounds
- all 5 bases in DNA and RNA
- 17/20 amino acids used in protein synthesis
- 3- and 6-carbon sugars
What is a "recipe for life"?
- 1. take early (pre-O2) atmosphere and zap with lightning - form monomers (amino acids, nucleotides, sugars)
- 2. place monomers in locations favorable to condensation reactions (clay shores, hydrothermal vents, hot pools) - polymers (proteins, carbs, RNA/DNA, lipids)
- 3. RNA before DNA - simpler, acts as a catalyst
- 4. lipids naturally form bilayer spheres - encapsulae RNA providing more stable environment
- 5. self-replicating structure - nucleic acid inside and nucleotides on outside
how long ago did earth form?
how long ago did life originate?
how long ago did photosynthesis arise?
how long ago did eukaryotes arise?
how long ago did multicellular life form?
how long ago was the "Cambrian explosion"?
When did life on land begin?
When did the first humans arise?
What are some examples of physical changes to earth that happened over time?
- movement of continents - continental drift
- volcanic activity, meteorite collisions
- rise and fall of sea levels
- changing temp
- increase in O2
What's an example of a physical change that life brought to Earth instead of the other way around?
Produced an increase in O2
how did photosynthesis arise?
- early atmosphere had no oxygen
- light energy splits water, organisms used free electrons to reduce carbon dioxide and build organic molecules
- oxygen is a waste product
- leads to aerobic respiration
- leads to more complex life (eukaryotic, multicellular)
Which species evolved photosynthesis first?
Cyanobacteria - photosynthetic prokaryotes, formed stromatolites
What is the precambrian era?
- lasted from ~4.5bya to 542 mya
- largely unicellular, prokaryotes
- life confined to oceans
What is the paleozoic era?
- "old life"
- lasted from 542mya to 251mya
What is the mesozoic era?
- "middle life"
- lasted from 251mya to 65mya
What is the cenozoic era?
- "new life"
- from 65mya-present
in which geological era did stromatolites form?
- (layered cyanobacterial concretions
- in the precambrian era
When did eukaryotes evolve?
late precambrian (last 1/3 of era)
What are "Ediacarian animals"?
larger soft-bodied animals
when did Ediacarian animals evolve?
late precambrian era (last 1/3)
How does the paleozoic era begin?
begins with Cambrian explosion - relatively rapid diversification of multicellular life
What is Burgess Shale?
- In British Columbia
- discovered in 1909
- best fossil site of cambrian animals
- excellent preservation of soft and hard parts
Which group of animals is the most diverse and numerous?
What is the ordivician age?
- During paleozoic era
- radiation of marine organisms (like brachiopods and mollusks)
- ended with massive extinction (75% of species eliminated) because of sea level and ocean temperature drop
what is the silurian age?
- during mid paleozoic era
- marine life rebounded
- animals swim and feed above ocean bottom, jawless fishes diversified
- colonization of land (simple plants, arthropods like millipedes and scorpions among firtst)
what is the devonian age?
- during mid-paleozoic
- "age of the fishes"
- in oceans: fishes diversify - evolve jaws, loss of heavy armour, limbs & radiation of corals and shelled cephalopods
- on land: common are large club mosses, ferns and horsetails & first seed plants (gymnosperms) & spiders and insects
- ends with mass extinction (75% of marine life wiped out)
what is the carboniferous age?
- during late paleozoic
- 359-297 mya
- "age of amphibians or coral"
- amphibians diversify and are abundant
- land dominated by giant swamp forests (ferns and horsetails)
- insects evolve flight
- crinoids abundant in oceans
- amniotic egg evolves
What is the amniotic egg?
- a shelled egg with extra-embryonic membranes
- key adaptation that allowed organisms (like reptiles, birds, and mammals) to reproduce on land
- modifications exist across amniotic animals
what is the permian age?
- during late paleozoic era
- 297-251 mya
- reptiles diversify and begin to dominate over amphibians - many new lineages evolve
- largest mass extinction in earth's history (96% of life became extinct)
- oxygen concentrations dropped by 50%
what is the triassic age?
- during mesozoic era
- 251-200 mya
- early dinosaurs
- first mammals
- diversification of invertebrates
- ends with mass extinction (~65% of species go extinct)
what is the jurassic age?
- during mesozoic era
- 200-145 mya
- large terrestrial herbivores and predators are dinosaurs
- flying reptiles appear (pterosaurs)
- first fossils of flowering plants
- radiation of ray-finned fishes
what is the cretaceous age?
- during mesozoic era
- 145-65 mya
- dinosaur continue to diversify
- first snakes appear
- mammals radiate, but most small
Why was there a mass extinction during the cretaceous age?
- Probable cause - meteorite impact
- On land all animals >25kg became extinct, plus many insects
- Probably died because of lack of food
How do we know there was a mass extinction during the cretaceous age?
- 1. High concentrations of iridium (rare on earth, but abundant in meteorites)
- 2. Crater loacated off Yucatan, 180km in diameter and based on this size, estimate meteorite collision released 100 megatonnes of high explosives
What is the cenozoic era?
- 65mya - present
- "age of mammals"
- starts with the recovery from mass extinction
- radiation of birds
- radiation of flowering plants (angiosperms - evolve symbioses with nitrogen fixing bacteria, insects)
- radiation of mammals - hominids
When did our species appear?
About 200,000 years ago