History of Life on Earth (from module) Flashcards
what 3 changes had an influence on development life on earth
- Changes in the composition of the atmosphere
- changes in climate
- geological events
5 characteristics of changes in composition of the atmosphere
-3.5 billion years ago: no oxygen
-anaerobic bacteria was first living organisms
-cyanobacteria evolved same time anaerobic bacteria and able remove carbon dioxide from air and release oxygen
-levels of oxygen in atmosphere increased
-new life forms able to evolve
5 characteristics about changes in climate
-periods extreme cold followed by warm/very dry periods
-have been 4 ice ages
-ice age occurs when thick layer of ice covers majority earth
-ice forms, ocean levels decrease, land exposed
-ice melts, ocean level rise, lower lying areas of land flood
what is the proof that places were once covered by oceans
-bivalves and ammonites on Makhatini flats in KZN
-trilobites in karoo
6 characteristics of geological events
-earth divided into tectonic plates that move very slowly
-evidence of tectonic movement includes earthquakes, volcanoes, tsunamis
-movement of tectonic plates cause continental drift
-290mya Earth consisted on land mass called Pangea
-250mya mass separated into 2 land masses: Laurasia and Gondwanaland
-140mya continents as they are today
how do we know that the continents were once joined
many examples fossils found separate continents and nowhere else and modern-day distribution of certain animals also suggests some continents were joined before
biogeography
study of the distribution of species and ecosystems in geographic space and through geological time
how are eras characterised
rock types and fossils
what are the 3 mot recent eras
Paleozoic, Mesozoic, Cenozoic
when did the Cambrian period occur
545mya-495mya
what animals found Cenozoic era
humans and mammals
what species found Mesozoic era
dinosaurs, first birds, cycads, modern seed bearing plants
what species found Paleozoic era
reptiles, insects, crinoids, cartilage fish, earliest land animals, early bony fish
when did Cambrian explosion start
beginning of Paleozoic era
what was life like during Cambrian period
-warm climate many warm shallow seas
-no land animals
-large diversification of animals
-multicellular organisms hard exoskeletons common (trilobites)
-many algae, worm-like animals, molluscs, arthropods
-representatives almost all modern-day phyla present
mass extinctions
occur over relatively short periods time during which there is a dramatic increase in number of species hat die and disappear
what are the 5 periods of mass extinction
Late Ordovician, Late Devonian, End Permian, Late Triassic, Cretaceous-Tertiary Boundary
what causes a mass extinction
- climate change e.g. glaciation
- change in sea level
- continental drift
- meteorite/asteroid impacts
when was the most recent mass extinction
65mya
what are the 2 theories for Cretaceous-Tertiary Boundary mass extinction 65mya
meteorite impact theory and vulcanism in India
discuss/explain meteorite impact theory
-evidence giant meteorite striking earth (sediment found fossils)
- high iridium concentrations found in layer (iridium only found Earth’s mantle and meteorites/comets)
dust from meteorite impact blocked out sunlight for months, leading to plants death and consequently dinosaurs death
-oxygen levels dropped
-global temperature dropped
-additional carbon dioxide in atmosphere created acid rain
discuss/explain vulcanism in India
-evidence immerse volcanic activity found Deccan region
-iridium layer thought been pushed onto earth’s surface by molten rock
-lava released large amounts Sulphur dioxide into atmosphere
-atmosphere and oceans poisoned by falling acid rain
-wide spread fires occurred
-clouds ash blocked sun
-Earth’s temperature cooled
-little/no sunlight, photosynthesis slowed
-plants died, consequently dinosaurs died
-oxygen levels decreased, carbon dioxide level rose
-mass extinction of dinosaurs and other species occurred
what are the possible causes of the mass extinction at end of Permian period 250mya
meteorite impact (crate evidence NW Australia) or extended volcanic eruptions (evidence in Siberian traps) - 96% life died
how are humans impacting loss of biodiversity
(HIPPO)
-Habitat destruction (roads, buildings, crops, golf courses)
-invasive alien species
-population explosion of humans
-pollution
-over exploitation of natural resources
palaeontology
study of fossils
fossils
remains of living organisms preserved in rocks
where are fossils mainly found
sedimentary rock
how is sedimentary rock formed
sediment from rivers or from wind are laid down, thousands years layers pile up and weight presses down on layers below compacting and turning them into sedimentary rock
how are fossils formed
- sediment: animal buried by sediment (volcanic ash/silt) shorty after death. bones protected from rotting by layer of sediment
- Layers: mover sediment layer accumulate over years above animal remains and minerals (silica) slowly replace calcium phosphate in bones
- Movement: movement of tectonic plates/giant rock slabs that make up Earth’s surface, lifts up sediments and pushes fossils closer to surface
- Erosion: from river/rain/wind wears away remaining rock. erosion/people digging expose preserved remains
conditions needed for fossilization to occur
-animal die near water & covered silt before decomposition
-scavengers must not find/eat body
-sediment needs be acidic and contain no oxygen
-organism must have hard parts (bones, shell, fibers)
why is the fossil record incomplete
-soft-bodies organisms dont fossilize easily
-ideal conditions are absent
-some fossils difficult identify
-not all fossils have been found yet
what are the 4 types of fossil
- trace
- true form
- cast
- moulds and impressions
what is a true form fossil
made from actual plant/animal and original features remain intact
how are true form fossils preserved
hard body parts trapped under layers sand & clay. mineral particles replace hard body tissue. soft body parts decompose before fossilization can occur
examples of true form fossils
mummies, frozen mammoths, scorpion trapped in amber, Megalodon tooth, skull saber-tooth tiger
what is a mould/impression fossil
body plant/animal pressed between layers, leaving impression of its shape. surrounding mud & sediment hardens around dead organism and only imprint left after decomposition
examples of moulds/impressions
trilobite, fern leaf, early fish
what is a cast fossil
form from moulds. body trapped under layers of sand/clay which harden from rock. body & skeleton dissolve leaving impression on mould. mould filled other materials, forms cast
examples of cast fossils
cast of brain formed in the cranium
what are trace fossils
fossils leave records of the behaviors and movements of animals
examples of trach fossils
footprints, nests, faecal matter, Laetoli footprints, coprolite (dinosaur poop)
methods of dating fossils
- relative dating
- radiometric dating
- stratigraphic dating
- fluorine analysis
what is flourine analysis
flourine accumulates bones as fossilize. more flourine=older
what is stratigraphic dating
deeper layers considered older
what is relative dating
assumes fossils founds same layers are same age and that layers with similar fossils are same age
why is relative dating complicated
geological factors can cause faulting and tilting of rocks
what is radiometric dating
relies on decay of radioactive isotopes which happens at predictable rate e.g. Carbon-14 dating, Potassium-argon dating
isotope
atoms in some chemical elements have different forms which break down over constant rate
what are the commonly used elements for radiometric dating
argon, uranium, potassium, rubidium - fairly long half life
what is deductive reasoning
coming to decision/conclusion by using all information gathered e.g. age of fossil, age of surrounding rock, place fossil found
what is the most recent species to evolve
humans (2.3mya in Africa)
what is a transition fossil
any fossilized remains of a life form that exhibits traits common to both an ancestral group and its derived descendant group
archaeopteryx
transition fossil between reptile and bird
thrinaxodon
mammal-like reptile found karoo. dates back triassic period (240mya). link between reptile and mammal
archaeopteryx reptile features
-skull teeth and jaws
-no beak
-3 claws end of bones each wing
-sacrum made 6 vertebrae
-belly ribs
long boy sternum
archaeopteryx bird features
-feathers
-hollow bones
-wishbone
-3 forward facing toes and backward facing toe
what is a living fossil
organism remained essentially unchanged from earlier geologic times and whose close relatives are usually extinct
example of living fossil
Coelacanth, lobed-finned fish thought be extinct
world famous fossil sites
-cradle humankind
-west coast fossil park in Langebaan
-Kitching Fossil Exploration Centre in Nieu Bethesda
when was the taung child found
1925 in Taung North West
