14.1 Genetics and evolution

Question 1

When did the earth begin

Answer 1

Between 3 and 4 billion years ago

Question 2

What are fossils

Answer 2

Remains of organisms from millions of years ago that are found preserved in rocks or ice

Question 3

What are the three ways in which a fossil can form

Answer 3

• from parts of organisms that have not decayed because one or more conditions needed for decay are absent
• when parts of the organism are replaced by minerals as they decay
• as preserved traces of organisms, such as footprints, burrows and rootlet traces

Question 4

When does an animal or plant not decay after it has died

Answer 4

• little or no oxygen present (eg peat bogs which are acidic)
• poisonous gases kill off the bacteria that cause decay
• temperature is too low for decay to take place (eg ice)

Question 5

What is another example of evidence for evolution

Answer 5

Antibiotic resistance

Question 6

How is Darwin’s theory supported by fossils

Answer 6

• it has been shown that characteristics are passed on to offspring in genes
• there is further evidence in the fossil record and the knowledge of how resistance to antibiotics evolves in bacteria

Question 7

Why is the fossil record not complete

Answer 7

• earliest life forms were soft bodied organisms that left little fossil tace
• majority of fossils formed in the earliest days will have been destroyed by geological activities
• most organisms that died di don’t become fossilised because the right conditions for fossil formation were rare
• there are many fossils still to be found

Question 9

how are fossils made (6 steps)

Answer 9

1. an animal dies. some parts of the body and usually only the skeleton is left
2. the skeleton is covered with sand, earth, rock or seabed before the bones can disappear
3. over a very long time, the bones break down and leave a space in the earth, like an empty mold
4. minerals slowly fill the space in layers, in the exact shape of the bones
5. under lots of pressure, the new minerals harden into rock
6. the earth is eroded away by the weather or by the sea. the rock fossil exposed and discovered