Lecture 4 - Life on Earth Flashcards
List the 5 stages describing a rough picture of Earth over 4.6by
- Orange = Archaean = microbes
- Snowball = cooling, water, glaciation
- Dinosaur/Pangean = huge continents
- Last ice age
- Present/Holocene = last 10k yrs
List the 4 main eras of Earth and when they occurred
- Hadean = 3800-4600mya
- Archaean = 2500-3800mya
- Proterozoic = 500-2500mya
- Phanerozoic = present-500mya
Describe what the Hadean era looked like
Molten gaseous mass
What are the 3 theories of how prokaryotes emerged in the Archaean era? Is there any evidence of any of the 3 theories?
- Meteorites with simple organics that then replicated eg modern meteorites with glycine
- Spontaneous natural processes from reducing atmosphere, electricity, water etc until organics eg mimicked in lab
- Deep sea hydrothermal vents form protocells of double membrane around RNA and fatty acids eg found today
What are the features of prokaryotes that link them to a possible protocell origin?
Single celled, nucleoid, no organelles, thylakoid membrane for photosynthesis (cyanobacteria)
What are stromatolites and thrombolites and when did they exist? Why were they so important?
- Cyanobacteria bound in sediments and deposited in layers (stroma) or clumps (thrombo)
- Dominant organisms of proterozoic
- O2 production
Describe the theory of how eukaryotes emerged
Endosymbiosis = eu + pro with mitochondria = animal cell, eu + pro with chloroplast (cyanobacteria) = plant cell
What are the reasons behind why eukaryotes formed multicellular organisms? What is an example that proves this?
Avoid predation, functionality, share info about environment eg slime moulds either uni/multicellular but function better as multicellular
What and when was the Cambrian explosion?
- 540mya in Phanerozoic
- Marine animals evolved into modern body plans eg sensory systems, bilateral symmetry etc along with food web organisation
List in order the main evolution events of the phanerozoic after the cambrian explosion
- Simple land plants with pores instead of roots
- Amniotic tetrapods from sarcopterygii (fish with lobed fins) bc homologous structures
- Synapsids/mammals and sauropsids/reptiles and birds
- Marsupials and flowering plants
When was the Cretaceous-Tertiary extinction/K-T and what was the extinction rate?
65mya with 75-80% of all species
When was the Permian-Triassic extinction/Great Dying and what was the extinction rate?
250mya with 50% extinction = 100% trilobites, 90% marine species, 70% terrestrial vertebrates
What is geological history?
Changes in structure and formation of continents 1100mya-present
What are the 2 supercontinents in Earth’s history?
- Rodinia 1000mya covered most of planet -> Laurentia -> Gondwanaland
- Pangea 200mya -> modern continents
What is an example of evidence of Pangea splitting up?
Marsupials in Australia not found elsewhere after migrating to Australia before Pangea split up
What is biogeography?
Study of patterns of distribution of different life forms and explained by plate tectonics
List the 6 terrestrial regions
- Ethiopian = Africa
- Australian
- Palearctic = Europe
- Oriental = Asia
- Nearctic = North America
- Neotropical = South America
(7. Arctic)
List the organisms included as hominids and where the lineage comes from
- Humans, orangutans, chimps and gorillas
- Closely related to old world monkeys eg gibbons
- Humans share 99% genes with chimps
What are some of the recent findings with hominin fossils?
- Huge skull variation = unknown number of species
- Mixed DNA of different species eg Neanderthal x Denisovans = coexistence 40-50k yrs ago
