History Of Life On Earth Flashcards
Life exists in..
A huge array of FORMS and MODES of life.
Enormous biodiversity exists in Earth:
*endemism in Southern Africa
Large variety:
1. Species
2. Different ecosystems
3. Genetic differences
Endemism:
Indigenous but only found in 1 geographical space / area in country:
*hyper specific indigenous
Indigenous:
Comes from a specific country (native and originally found there)
Biodiversity:
The variety of organisms that can be found on earth as well as the interaction between them.
What is the first life form, that modern life extended from?
First bacteria: CYANOBACTERIA
(Blue/ green) : made photosynthesis possible
(First autotroph)
What are the changes in life forms related to?
*Climate change
*Movement of continents and oceans over evolutionary time
History of life on earth
The study of how organisms originated and diversified over time on our plsnet
Evidence to formulate history of life on earth:
- Geological events
- Geological rock dating
- Biogeography
- Fossil dating
Study of fossils:
Palaeontology
What is a common ancestor?
The original organism from which all life forms diverged and are then related to
Common ancestor for all life on earth:
ANAEROBIC BACTERIA
(Oxygen not required for life processes)
6 most important geological events that influences living things over time:
- Atmospheric oxygen content changes
- Continental drift
- Plate tectonics
- Volcanic activity
- Ice ages
- Meteorite / asteroid impacts
Changes in the composition of the atmosphere!
Increases in levels of oxygen
CYANOBACTERIA
Development of photosynthesising bacteria created current atmospheric composition:
*Cyanobacteria bacteria used CO2 in air and gave off O2 as byproduct of photosynthesis.
*Concentration of O2 starting increasing.
*As number of Cyanobacteria increased : CO2 concentration decreased.
*levels of N2 (nitrogen) in atmosphere increased.
- N2 in sea water used by Cyanobacteria to make PROTEINS
Increased O2 and increased UV exposure = OZONE LAYER around planet
What is the green house effect?
A good process whereby the Earth is kept warm
Most common greenhouse gases:
Methane
CO2
Nitrous oxide
Effect of too much greenhouse gases:
Leads to:
1. Global warming
2. Green house effect
(Harming earth)
What does the enhanced greenhouse effect lead to:
Climate change & Global warming
- disrupts ecosystems and decreases biodiversity
(currently: 6th maths extinction)
Ice ages:
*Long periods of extremely low temperatures leading to Earth covered in glaciers and ice sheets.
- sea levels were low: water trapped in glaciers
- habitats of marine species decreased
-species who were not (FIT) for dry conditions : did not survive
*once temps increased, ice caps melted = increase in sea levels
Survival of the fittest:
NATURAL SELECTION
- affects biodiversity and changes composition of ecosystems : affecting energy flow of organisms.
Geological events : continental drift
- Earth’s continents were once joined as 1 supercontinent : PANGAEA
- Drifted apart (plate tectonics) : LAURASIA (N) & GONDWANALAND (S)
- 7 continents
plate tectonics refers to:
Movement of tectonic plates under Earth’s crust.
*when join/ rub: EARTHQUAKES OR VOLCANIC ACTIVITY occur
(As tectonic plates move: continents move)
Change in animal distribution influenced by:
Continental drift
Define: Biogeography
The study of the distribution of organisms on various continents over time.
Changes in sea level: RISE AND FALL OF LAND
As sea levels change: amount of available land changes
*Decrease: glaciation
*Increase: melting glaciers
Evidence supporting:
-Sahara: whale fossils
-Karoo: trilobites
Why do volcanic eruptions take place?
- Continental drift
- Large meteorites & comets hitting Earth surface
Impact of volcanic activity:
- Release ash and dust: blocks out the sun — cooling down of earth — glaciers — decrease sea levels
Effect on photosynthesising plants:
*Photosynthesis CANT take place : light unavailable to plants
- Increased : CO2 / decreased : O2
- Scarcity of food : life died off
- Mass extinction
- Dust settled — increased CO2: enhanced greenhouse effect
- Warming earth : melting ice caps
- Sea levels rose
- Photosynthesis could OCCUR once again.
Meteorite and comet impacts:
Large meteorites (300km) impacted surface of Earth.
*Molten lava came up from Earth’s core and destroyed large ecosystems
- volcanic eruptions
Organism divergence from common ancestor:
All organisms came from a common ancestor that changed over time due to:
1. Changes in enviro
2. Mutations
Define Mutations:
Sudden changes that occur in the genetic make-up (DNA) of organisms
Explain Diversification:
Species diverged from each other as number of mutations increased
Process of speciation:
Not able to INTERBREED and became separate species from each other.
(Number of Species increased)
2 trends in changes evident over evolutionary time:
- Aquatic organisms came before terrestrial organisms in time
- Simple organisms came before complex organisms in time
Define : Geological time scale:
A record of the formation of rocks and the appearance of organisms over geological time
THREE ERAS (geological time scale):
- Paleozoic era - (period: cambrian)
- Mesozoic era - (triassic)
- Coenozoic era - (tertiary)
The meaning and use if time scales:
Used by: geologists, palaeontologists and scientists
- Describe the timing and relationships of events that have occurred during Earth’s history.
(Geological time)
Define fossils:
Fossils are the remains of organisms which died thousands of years ago and were preserved in specific rock layers. (Dried sap: amber / ice, tar)
(Palaeontologists)
Geological rock dating function
Fossils are embedded in rock layers
- age of rock layer = age of fossil
Explain the CAMBRIAN EXPLOSION
- Rapid DIVERSIFICATION of organism and increase of : varied species
- During Cambrian period: Earth’s conditions = favourable for life : number of species diversified quickly.
Why is the Cambrian explosion important?
Gives insight into origins of major forms of all animal groups
2 types of extinction:
- Biological extinction
- Mass extinction
Define: Biological extinction
All individuals of a single species or a few species die off at roughly the same evolutionary time
Define: Mass extinction
- Large number of species die out at same evolutionary time
- Over thousands of years
- 5 mass extinctions occurred over geological time (Earth history)
- Present Rate of extinction: higher than ever
(6th mass extinction)
5 mass extinctions in past
2 MOST IMP:
- 250 mya: (extinction of 90% of life)
- 65 mya: (extinction of many species & Dinosaurs)
Dinosaurs were largest mammal in Earth
- their extinction allowed animals to diverge : ECOLOGICAL NICHES
Ecological niches:
An ecological niche is a species’ role in its environment. Diversification happens as species adapt to different niches, reducing competition and leading to the evolution of new species.
Sequence of Vertebrae classes
(Least evolved —> most evolved)
- Fish
- Amphibia
- Reptilia
- Aves
- Mammalia
How are fossils formed?
Fossils are only found in: Sedimentary rock
* The closer the organism to an aquatic environment, the more likely to fossilise over time
(Decomposes soft parts: mud)
Process of fossilisation:
- Organism dies
- Covered by sediment (sand and water = sediment)
- Soft parts of body decomposed by microorganisms (bacteria)
- PERMINERALISATION: minerals of sediment move into hard parts of body (bones/shell)
- Soil gradually added in layers
- Weight of soil: compacts bottom layers (compression)
- Sedimentary rock layer formed : permineralized parts of organism in it
- Over time: fossil formed in sedimentary layer
- Older fossils : older rock layers
Define: transitional fossils
Fossil that show characteristics of two different groups of organisms which follow in sequence over evolutionary time.
One group is more primitive (preceding) & other more advanced
(2 groups in succession)
The fossil record:
All fossils that have been found in world are part of fossil record.
The fossil record:
All fossils that have been found in world are part of fossil record.
Fossil record: DISADVANTAGES (evolution)
incomplete
- Mainly hard-bodied organisms are represented in fossil record
(Not all soft bodied organisms in resin were found) - Gaps in record: affecting interpretation of origin of species over time
(Mining & excavation) - If hard- bodies organisms died far from water source: did not fossilise
- Did not fossilise in one place
(Animals carried bones: skeletons scattered)
Fossil record: DISADVANTAGES (evolution)
incomplete
- Mainly hard-bodied organisms are represented in fossil record
(Not all soft bodied organisms in resin were found) - Gaps in record: affecting interpretation of origin of species over time
(Mining & excavation) - If hard- bodies organisms died far from water source: did not fossilise
- Did not fossilise in one place
(Animals carried bones: skeletons scattered)
Fossil record: ADVANTAGES (evolution)
- Anatomy of fossils help classify and determine age
(Simple organisms before complex organisms)
( descent by modification / natural selection: CHARLS DARWIN - As new fossils are found: compared to existing fossils
- Transition fossils
(Supports Darwinism: species transitioned from one group to next)
Understanding fossils:
Scientists use DEDUCTIVE REASONING (interference) to understand fossils and history of life on Earth
Understanding fossils:
Scientists use DEDUCTIVE REASONING (interference) to understand fossils and history of life on Earth
Function of fossil dating and types:
Determine age of fossils
- Relative dating
- Absolute dating
Relative dating:
- Used before modern technology
- index fossils used to determine age of other fossils : comparing relative to age of index fossils
INACCURATE
Why are index fossils used?
- Widely distributed
- Many occur
- Age is well documented and existed in short space of time
Absolute dating
(Radiometric dating)
RELIABLE & ACCURATE
*dates rock layer: fossil found in specific rock layer
Transitions into daughter element through radioactive energy loss
Parent element/ isotope
Radioactive
- Unstable
- Decays / loses radioactivity at a fixed rate over time known to scientists.
Parent element/ isotope
Radioactive
- Unstable
- Decays / loses radioactivity at a fixed rate over time known to scientists.
(Measured in half lives)
Parent element/ isotope
Radioactive
- Unstable
- Decays / loses radioactivity at a fixed rate over time known to scientists.
(Measured in half lives)
Daughter element
Stable element formed by radioactivity loss of parent isotope
Define: one half life
The amount of time it takes for the radioactive isotope to lose half of its radioactivity
What is fossil tourism?
A source of income, national and local pride and employment in some areas
Fossil tourism: ECOLOGY
Advantage: promotes awareness and conservation of fossils & ancient ecosystems
Disadvantage: habitat disruption and degradation of natural sites
Fossil tourism: FINANCES
Advantage: generate income for local communities and supports economy
Disadvantage: over reliance on tourism harms local economy if sites are exhausted
