B15 Genetics and Evolutionn Flashcards
A large amount of our understadnings of genetics came from what monk ?
-Gregeor Mendel
What experiment did Gregor Mendel carry out ?
- Mendel carried out thousands of breeding experiments on pea plants .
- At this time , scientists did not understand how inheritance worked .
- He looked at many different characteristcs 0 shape of the pod and colour of flowers .
How did scientists back in the day believe characteristics were inherited ?
-Many believed that characteristics were blended when they were inherited .
What did Mendel conclude from his experiments ?
- That characteristics were not blended during ineritaince (the shape of a pea pod has no effect on the colu .
- Mendel said characteristics were determined by units .
What were the units Mendel was talking about ?
These units do not change when passed onto descendants .
-These units are called genes .
What other conclusion did Mendle have from his experiment (2)
- He showed some characteristics could be masked and hten reappear in later generations .
- These are now knon as recessibe alelles .
Why didn’t scienitsts believe mendel ?
- Mendel published his research in a scientidic paper .
- But many scientits still held onto the idea that chaacteristc were blended when inherited and his discovery was forgotten .
How did Mendel’s discovery be remembered again ?
- In the 1800s , scienits looked at how chromosomes behaved in cell divion . Then scientists rediscovered Mendels work on geentics .
- By 1900s , scientists realised that Mendel’s units behaved in a simialr way to chromosomes .
What happened in 1900s
-This time thereofre , Mendel’s units renammed genes , and scientists realised genes must be lcoated on chromosomes .
What happened in 1859 ?
-Darwin publishedhis theory in a book called the Origin of Species .
Why was Darwin’s theory extremely controverisial ?
-In early Victorian ENgland , lots of people strongly believed that God made all animals and plants that lived on Earth . Darwin’s thoery challenged that belief .
Why was Darwin’s theory extremely controverisial ? (2)
-At the time , a lot of people strongly believed that God made all animals and lants that lived on Earth . Darwin’s thoery challenged that idea .
Why was Darwin’s theory extremely controverisial ?(3)
-At that time , many scientists felt that Darwin did not have enough evidence to back up his theory .
Why was Darwin’s theory extremely controverisial ? (4)
-People did not understand how characteristics are inherited . (Genetics not understood until 50 years after Dawrin’s thoery was published)
What did Alfred Russel Wallace do ?
- He travelled looking at different animals and plants .
- he was interested in warning colouraiton and wanted to know hwo warning colours evolved .
What happened in 1858
- Charles Darwin and Alfred Russel ahd the same findings about natural selecion and jointly published there findings .
- Next year , Darwin published ‘on the origin of species’
What is speciation ?
-How new species form .
-What did Wallace notice ?
He noticed that closely related species were often separated by geographical barriers such as a wide river .
What needs to happen for speciation to take place ?
-There has to be a geographical barrier which separtes the populations into two grougps ,which prevents interbreeding between the two populations .
- How species formed in depth
-A place containing one species of animals , all these animals interbreed , so any beneficial muation spreads thorugh the howle population .
- How species formed in depth
- A geographical barrier (river) , separates that species of animals into two groups .
- How species formed in depth
As two populations are now separated , there is no interbreeding between the two groups .
- How species formed in depth
- Overtime , natural selection , will favour different alleles in both groups (the food source may be different on one side compared to the other .)
- How species formed in depth
As there is no interbreeding between the two populations , any mutations that occur cannot spread between the two populations .
- How species formed in depth
This means over many generations , the two populations of that species will begin to change .
- How species formed in depth
-If the geographical barrier goes away the two populations of that animal can mix .
- How species formed in depth
-At this point the phenotypes of the two poulations are so different , they can no longer reproduce to make fertile offspring .
- How species formed in depth
Now those two groups are two different species .
What was Jean Baptiste Lamark’s theory ?
- He noticed that animals seemed well sutied to their enviornment and suspected thorugh their lifetime they would improve themselves .
- (e.g giraffe’s long neck was sue to it streching for food higher and higher .)
What was Jean Baptiste Lamark’s theory (2) ?
-Lamark also thought these changes caused byt he animals struggle was passed onto the ext generation which hten continued the evolutionary process .
What was the difference in Charles Darwin and Lamark’s ideas ?
-In Darwin’s idea , the traits of the parents were passed on without being modified by the life of the parent (state Lamark’s theory).
What did Darwin realise on HMS Beagle ?
-That in any populaiton of a living organism , there already exists variation in any given characteristic .
What did Darwin realise on HMS Beagle ? (2)
- Reproduction always gives more offpspring than the neviornent can support .
- The organisms that have inherited the characteristics most suited to their environment - the ‘fittest’ are more likely to survive and breed successfully .
What did Darwin realise on HMS Beagle ? (3)
- When they brred , they pass on the characteristics that have enbaled them to survive to the next genration .
- He also proposed changes in a species happens very gradually .
What are fossils ?
-Fossils are remains of organisms from millions of years ago which are found in rocks .
-What is one way fossils form ?
-Fossils can form when parts of organisms have not been destroyed . Can happen whn the conditions needed for decay are absent . (temperature cold , lack of oxygen and water ).
-What is another way that fossils form (2)
- Fossils can be the preserved traces of organisms .
- Animals can leave footprints or burrows and plants can leave preserved psaxces were roots were .
What is the problem with fossils ?
- Many of the earliest forms of life were soft bodied organisms .
- Soft bodied organisms evry rarley form ossils .
- Many of the fossils that did form have been destroyed by chages in rock in the Earth’s crust .
What is the meaning of soft bodied organisms ?
-Organisms that don’t have sheels or skeletons .
Why can’t cientits be certain how life on Earth begain ?
-As there are very few fossils of the early forms of life .
What is the meaning of extinction ?
- Extinction is when there are no remaining individuals of that species stil alive .
- Fossils can show huge numbers of species that have become extinct .
What is one reason for extinction ?
- Species can become extinct due to a catastrophic event .
- Asteroid colliding with Earth eventually lead to extinction of dinosaurs .
What is another reason for extinction ? (2)
-Sometimes , as pecies can become extinct when the environemnt chnages e.g changing weather patterns .
What is another reason for extinction ? (3)
-A new disease or new predator could kill all the individuals of a species and make it extinct .
What is another reason for extinction ? (4)
- A species can become extinct if a new or more successive species eveloves nd competes with it .
e. g for food sources or scarceness of water.
As more species were discovered , what did scientists realise ?
-Those species have characteristics in comon .
In the 1700s , what did Carl Linnaeas do ?
-He bagan to classigy species into different catgeroies based on their structure and characteristics .
What did Liinaes divide all lviging organisms into ?
1.He divided all living organisms into two kingdoms . These are the ANIMAL kingdom and the PLANT kingdom .
2. He then divided each kingdom into number of smaller catgeories .
Kingdom , Phylum , Class, Order , Family , Genus , Species (King phillip came over for good soup ).
How is every organism named ?
-From their genus and their species
This is known as bionomial name .
-What is the meaning of a bionomial name ?
-Two names
-How do you work out the bionomial name ?
The one with the capital letter is the first name /Genus
What is Linaeus’s classification based on ?
-Based on characteristics we can see (shape of body , number of toes ).
What classification sytem do scientists use now ?
They use the three domain sytem :
- Archae
- True bacteria
- Eukaryotic
Explain Archae
- Archae are primitive (early stage ) bacteria .
- They are found in extreme conditions such as hotsprings .
Explain True bacteria
-Kind that live in human digestive systems .
Explain Eukaryota
-Include animals , plants , fungi and protists .
What are evolutionary trees ?
Scientists use them to show how clsely related organisms are to eachother .
What do you need to make an evolutionary tree ?
-Need classification data on living organisms such as DNA .
How do you do evolutionary trees for extinct animals .
What is the problem with this ?
- Scientits have to use fossils .
- The fossil records of many species are incomplete .
Look at the evolutionary tree on the page make three comments /
- Species one and two are closely related to eachother .
- Species three is more distantly related .
- But species 1 , 2 and three all share a common ancestor .
