Old And New Species Flashcards
When did life begin on earth?
3500 million years ago
How can we date when different organisms existed?
We can date the rocks that the fossils are found in
How can fossils be formed?
- The hard parts of animals do not decay easily eg teeth, bones, shells, claws
- from parts of organisms that have not decayed because some of the conditions for decay were absent e.g fossils of animals preserved in ice
- when parts of an organism are replaced by other materials, such as minerals as they decay
- as preserved traces of organism eg footprints, burrows, root let traces
Why are there no traces of early life forms?
They had soft bodies so decayed leaving few traces behind
How were the few traces left from early life forms destroyed?
Geological activity such as earthquakes
How would 4500 million be written in standard form?
4.5 x 10 to the power of 9
What does extinction mean?
A species which once existed has completely died out
What can extinction be caused by?
A new disease may kill all members of a species
The environment changes over geological time
New diseases may be introduced
A new predator may evolve or be introduced to a new area
A single catastrophic event may occur which destroys the habitat e.g a massive volcanic eruption
Natural changes in species occur over time
What can the fossils records show?
How little or how much an organism has changed over time
How can a new predator cause extinction of a species?
It eats all the animals
What is a very important factor in determining whether a species will survive?
Climate change, a species adapted to a hot climate may become extinct in the ice age as there may be insufficient food or are unable to breed.
What has fossil evidence suggested about why mass extinction occurs?
The habitat the species lives in may be destroyed by catastrophic events such as a major volcanic eruption
The environment can change dramatically following a collision between a giant asteroid and earth
What ideas have scientists suggested about why dinosaurs became extinct?
- The collision of a giant asteroid caused huge fires, earthquakes, landslides and tsunamis. The dust which rose masked the sun causing darkness and lower temperature. Plants could not grow
- the extinction was a slower process due to sea ice melting and cooling the sea temperature to about 9 degrees therefore there was less plankton, less food available
Suggest another factor that could have led to the dinosaurs dying out
A new disease introduced, unlikely a new predator as dinosaurs were at the top of the food chain
What is geographical isolation?
When 2 populations become physically isolated by a geographical feature
how could a species be separated?
- an island separates from the mainland
- a new river separates two areas
- mountain rage separates areas
- old craters isolate organisms
What will happen in the 2 populations?
They may be exposed to different conditions (food availability, climate, predators) natural selsction will occur in both populations so different characteristics will be beneficial to the two populations
Explain the process of speciation
6 mark
- new species will occur following the separation of 2 populations due to geographical isolation
- each population has a wide range of alleles that comtrol their characteristics (genetic variation)
- natural selection will occur in each population, the alleles that control the chacteristics which help the organism to survive are selected. The organisms with these alleles survive to breed
- if the environment, competitors, food supply and predators are different for each population they will evolve differently
- speciation has occurred as the two population can no longer successfully interbreed
Explain the process of speciation with 5 terms
Isolation -> Variation -> Alleles selected -> Interbreeding no longer possible -> New species
What is meant by genetic variation?
The wide range of alleles that control the characteristics in a population
How old is the earth?
4500 million years old
What is the theory of evolution?
Variation because of mutations
So are better adapted to their environment
Survive to breed
And pass on genetic information to offspring
What is a fossil?
The remains of an animal from many years ago left in rock
Describe one way in which fossils are formed
- hard parts don’t decay
- no decay as conditions absent
- parts replaced by rock minerals or chemical as they deca
What does extinct mean?
All organisms have died out
Reasons why an organism may become extinct?
Environment changed New disease New predator New disease New competitor Shortage of food Mammoths reproduced too slowly Mammoths did not adapt to changes
Explain how ….. Supports the theory of evolution
Present species evolved from earlier species Over long period of time Via many gradual changes Which gave survival advantage Passed on genes
Which is the most common type of fossil?
The fossils formed when When the harder parts of the animal or plants are replaced by minerals over time as they decay
What is it impossible to know how life on Earth began for sure?
Now scientists appt that time
Gaps in the fossil records
Earliest life forms were soft bodies and did not have fossils
Little valid evidence
How do ice fossils help scientists check the evidence provided by the main fossil record?
They can improve accuracy and tell us other things such as the colourings of a plant or animal or what it ate
We can also extract DNA from these ice fossils
How many species of living organisms are thought to have existed on earth over the years?
4billion
Why are ice ages often linked to extinction?
Climate changes cause many species to be wiped out in things like the ice age due to lack of food, too cold to breed and so will die
What is mass extinction?
Extinction on a global scale when many species in the world all die out
Give two possible causes of mass extinction
Catastrophic events like a volcanoe or collision of giant asteroids
Sudden change in environment, ice age
Why is extinction an important part of evolution?
Because it’s the animals that are no longer suited to an enviroment that become extinct, so more advanced creatures can take their place and thrive.
What is the evidence that suggest the dinosaurs caused mass extinction of the dinosaurs?
They found rock from long ago formed from lots of minerals which only come about a rock is hit with such force
This caused dust to rise blocking the sun causing plants to die out
Drop in sea temps
What is an endemic organism?
When a species evolves in isolation and is found in only one place in the world; it is said to be endemic to that particular area
What limitations do fossils have?
You are limited by current technology in how to get information out of them. You cannot tell about the life of an organism by finding one fossil because it’s a snapshot. You need to collect many of them. Also, you cannot tell when the fossil is from down to the exact year.
How does evolution take place?
Variation occurs caused by random mutation
The best adapted survive by natural selection and breed passing their genes to their offspring
