Cycle 10 - Diversity of Life Flashcards
Approximately how old is the Earth?
4.6 bya
How can the age of Earth be determined?
Radiometric dating - rate of rock decay
What do the four essential macromolecules tell us about the first cells?
- nucleic acid, proteins, carbohydrates, lipids
- first cells must have some of these essential macromolecules so simpler forms of them must have existed before cells
- abiotic synthesis
What did the atmosphere look like 4 bya? What molecules were present?
hot surface = water vapour
H2, CH4, CO2, NH3
almost complete absence of O2
Why was the early atmosphere considered a reducing atmosphere? What does this indicate for the evolution of the first cell?
RA = large concentration of H2, NH3, CH4 etc
so large complex ORGANIC molecules could form to create macromolecules because of the present molecules bonding capabilities
What is today’s atmosphere classified as? How does this compare with reducing atmosphere?
OXIDIZING ATMOSPHERE
- large complex organic molecules cannot form because large presence of oxygen = oxygen react = everything reduced to water
What is the impact of the Ozone layer (O3) in the young and present atmosphere?
Present: ozone layer present
Young: ozone layer not present = UV light and lightening able to provide energy for macromolecule creating reactions why reaching lower atmosphere
What was the Miller Urey experiment? What did it prove?
reducing atmosphere apparatus
- gaseous inorganic molecules sparked with electrode energy and boiling water for early water cycle
- showed that organic molecules did form (amino acids, fatty acids, sugars, phospholipids)
What is the clay hypothesis?
clay has a thin layer of minerals, a charged surface allowing for the formation of short polymers of proteins and nucleic acids prior to enzymes in the early Earth
What environment must have the first cells originate from?
ocean floor at the sites of alkaline hydrothermal vents
Why do scientists believe alkaline hydrothermal vents are where first cells originated?
- water temperature 100ºC-150ºC
- rich in molecules
- strongly alkaline
- calcium carbonate chimneys that are honeycombed with microscopic pores that water can move through
What are the seven common features for all forms of life on earth?
- Cells with lipid bilayer membrane
- DNA genetic system
- Central Dogma
- Ribosomes for protein assembly
- Proteins for as the major structural and catalytic molecule
- ATP chemical energy currency
- Common pathways of energy transformation
as well as ~ 50 genes
What are the two majoy distinctions between eukaryores and prokaryotes?
- seperation of DNA and cytoplasm by a nuclear envelope
- membrane-bound organelles (mitochondria, chloroplasts, EF, golgi complex
Why was cyanobacteria essential to Earth’s development/species?
photosythetic bacteria created oxygen so aerobic species evolved and greater amounts of ATP could be generated for breaking down glucose molecules (step towards eukaryotes)
What is the endosymbiosis model for mitochondria and chloroplasts?
Prokaryotic ancestors of mitochondria and chloroplasts were engulfed by large prokaryotic cells that formed a symbiotic relationship between them and the host cell
What evidence is available for mitochondria and chloroplasts to derive from prokaryotic bacteria?
- shape and size are similar to prokaryotic cell
- cells cannot synthesize mitochondria or chloroplast, instead they divide from preexisting in through binary fission
- contain their own circular DNA
- contain ribosomes and tRNA for transcription and translation
- Electron transport chains and ATP synthase for chemical energy
- Sequencing analysis shows chloroplasts are similar to cyanobacteria and mitochondria is similar to heterotrophic bacteria
What does the fact that chloroplasts are only in plants tell us about the endosymbiosis timeline for chloroplasts and mitochondria?
mitochondria first, chloroplasts second
What is the hypothesis for eukaryotes developing membranes around organelles?
infolding plasma membrane surrounded nucleus and formed ER
What is vertical gene transfer?
inheritance from one generation to the next
What is horizontal gene transfer? What is an example of this?
movement of genetic material between organisms other than by descent
ex. bacterial endosymbiosis
When the mitochondria/chloroplasts fused, how were their genetic material integrated?
- redundant genes were lost
- many genes in the proto-mitochondrion and protons-chloroplast were relocated to nucleus
What is strata? What is their importance in fossils?
layer of sediment of different colours, mineral composition that can show fossils from lowest/oldest to highest/newest
What are the characteristics of LUCA?
- cellular
- prokaryotic and likely bacterial
- anaerobic (doesn’t need oxygen b/c oxygen was scarce)
- autotrophic (synthesize sugars using chemical energy from vent for food)
What were the evolved characteristics from bacteria to archaea?
cell membrane/cell wall
How long was life on earth only microbial?
first 3000 mya
When was the first approximated archaea?
3500 mya
What were the evolved characteristics from archaea to eukarya?
membraneous structures in cell, mitochondria, mitosis & meiosis
When were the first approximated eukaryotes?
2000 mya
What bacteria did mitochondria descend from?
heterotrophic bacteria
- carbohydrate-eating, aerobic bacteria
- could not make its own sugars and uses oxygen which is why eukaryotes need oxygen
When did the first multicellular organisms evolve?
~1000 mya
What are opisthokonts?
group of eukaryotes that includes animals
What are chordates? When did they evolve
animals with dorsal nerve cords; 565 mya
What was the Cambria explosion? When did it occur?
sudden appearance of complex animals in fossil record occurring 540 mya
Which eon and era did the Cambrian explosion border?
end of Precambrian eon and Proterozoic era
start of Phanerozoic eon and Paleozoic era
What and when was the Ordovician-Silurian mass extinction?
440 mya when 85% of sea life was lost (oldest known mass extinction)
When did animals appear on land?
400 mya
What was the Late Devonian mass extinction?
370 mya when 75% of animal species was lost and vertebrates did not appear for 10 mya in the fossil record
What and when was the permian extinction?
250 mya when 96% of animal species lost at the end of the Paleozoic and start of the Mesozoic era
What and when was the Triassic-Jurassic mass extinction?
200 mya when 50% of species lost and dinosaurs dominated the plant
- habitats blend for dinosaurs and early mammals to evolve
When did dinosaurs go extinct?
65 mya Cretaceous-Tertiary mass extinction
Where does the placenta evolve from?
retroviruses infected mammal ancestor
- the retrovirus envelope gene called syncytin promoted cell fusion creating placenta cells
What and when was the Cretaceous-Tertiary mass extinction
65 mya when 75% of animals And plants lost including dinosaurs and the end of the Mesozoic era and start of Cenozoic era
What was the cause of the Cretaceous-Tertiary mass extinction?
asteroid caused climate change
What was the result of the Cretaceous Tertiary extinction?
opened habitats for mammal diversification (Age of Mammals)
When did primates first evolve?
after cretaceous tertiary mass extinction (63 mya)
When did great apes first evolve?
orangutans 14 mya
gorillas 7 mya
chimpanzees and bonobos 6 mya
When did homo sapiens first evolve? From where?
0.2 mya from Africa to Europe Asia and North America
What characteristics makes humans unique to other primates/great apes?
- bigger brain
- upright posture
- bipedal
- Flexible and precise grip
- Hairlessness
- Blushing
- Social and cultural cognition
- Language
Did humans evolve from chimpanzees?
No! Humans did not evolve from any presently existing ape; all apes come from a preexisting ape ancestor
Did Homo sapiens coexist with other homindae species?
Yes - Neanderthals and denisovans for thousands of years and they probably interacted with one another
Were the coexisting hominin species all one or several species?
since human genomes have DNA sequences in common with Neanderthals and Denisovans and they likely interbred it is possible (BSC)
What is the ecological-intelligence hypothesis?
tackle environmental challenges such as finding food, tool use, language, planning for survival is why humans have larger brains
What is the social-intelligence hypothesis?
competitive and cooperative challenges of living with other members of the same species for success is why humans have larger brains
What is the cultural intelligence hypothesis?
combines the ecological and social hypothesis for cooperative hunting and building shelter is why humans have larger brains
What is the mating mind hypothesis?
bigger brain for mating success (intelligence is attractive - art, humour, music) or as an elaborate structure
