7. Changes in biodiversity over time Part 1

Question 1

What is the continental drift theory, how does it occur, and what does it cause? Give an example:

Answer 1

States that the continents have moved and are still moving today.
-Continental drift occurs as the plates of the Earth’s crust move. This is called plate tectonics and causes earthquakes, volcanoes and the formation of mountain ranges.
Eg. 20 mya a supercontinent, Pangea, existed and subsequently broke up to form Laurasia and Gondwana.

Question 2

What was Pangea?

Answer 2

A super-continent

Question 3

Which countries did Laurasia include?

Answer 3

North America, Asia and Europe

Question 4

Which countries did Gondwana include?

Answer 4

Antarctica, Australia, New Zealand, Africa, India, and South America

Question 5

What are fossils?

Answer 5

Are the relic or impression of an organism from the past, usually preserved in rock.

Question 6

What are trace fossils? Give 2 examples:

Answer 6

Are fossils that show traces of organisms.

Eg. Footprints or teeth marks.

Question 7

What are living fossils? Give an example:

Answer 7

Are organisms still living today that have not changed from their ancestors.
Eg. Crocodiles

Question 8

What is a mold?

Answer 8

Shapes or impressions formed in rocks after the decay of an organism.
-Molds may fill with another sediment, making a cast

Question 9

Where are most fossils found?

Answer 9

Most fossilised ‘hard parts’ of animals or plants are found in rocks that have been derived from sediment- sand, stilt or clay.

Question 10

List and describe the specific requirements for fossilisation:

Answer 10

• Quick burial: Reduce exposure to environment, scavengers and decomposers
• Cold/hot temperatures: Protect remains from decomposers
• Anoxic environment (no oxygen): Remains are protected as aerobic decomposes cannot survive without oxygen
• Sap: Protects organisms from decay (much rarer and only for small animals or insects)

Question 11

Describe an example of fossilisation:

Answer 11

1. A dead organism is buried in stilt
2. Slowly decays and dissolves, leaving a space in the stilt
3. Minerals seep into space and solidify in the shape of the organism
4. The stilt also solidifies, turning into rock. A fossil has been formed, embedded in rock.

Question 12

What are transitional fossils?

Answer 12

Fossils that have characteristics that are intermediate in nature to organisms that existed both prior to it and after it.

Question 13

What is gradualism?

Answer 13

A theory of evolution that assumes that slow and steady changes occur in organisms over time.

Question 14

What does punctuated equilibrium refer to?

Answer 14

A theory of evolution that assumes that species remain fairly stable for periods of time but undergo changes in rapid bursts.

Question 15

List the 2 fossil dating methods:

Answer 15

• Comparative dating (relative dating)

- Absolute dating

Question 16

What is the principle of superstition in relation to relative dating?

Answer 16

Method of determining the relative ages of rock strata based on the principle that relatively older strata lie below relatively younger strata.

Question 17

Describe an example of the principle of superstition in relation to relative dating:

Answer 17

• There are a few theories about the exact cause of the dinosaur extinction at the K-T boundary, but believed to be due to an asteroid or comet impact with earth (where K: Cretaceous period, T: Tertiary period)
• Caused a large cloud of dust to cover Earth along with a rare (on Earth) element, iridium, that is found in asteroids
• A thin layer of iridium found all over the Earth in a layer that corresponds to the K-T extinction event

Question 18

Explain how dating layers in rocks works:

Answer 18

Layers can be dated using an indicator or index fossil (a fossil of known age found in a particular sedimentary rock layer) which can be used to indicate the age of the deposit at any single locality in which it is found.

Question 19

What is the principle of correlation in relation to dating layers in rocks?

Answer 19

Method of identifying rock strata in different locations as having the same relative age because of the presence of a particular index fossil.

Question 20

What is absolute dating?

Answer 20

A technique that assigns a numerical age in years to a fossil or rock.

Question 21

List the 3 methods of absolute dating:

Answer 21

• Radiometric dating
• Electron spin resonance
• Luminescence (Thermoluminescence and Optical Stimulated Luminescence)

Question 22

What is radiometric dating in relation to absolute dating?

Answer 22

A technique for obtaining the age of objects that depends on the known rate of decay of a radioactive parent isotope to a stable daughter product.

Question 23

What is a half-life?

Answer 23

The time it takes for half of the parent radioactive element to decay.

Question 24

Give an example of radiometric dating in relation to absolute dating:

Answer 24

Carbon-14 half-life is 5568 years. If you had 1.0g of Carbon-14 today, in 5568 years you would have 0.5g. (Useful for ages up to about 60 000 years)

Question 25

What does electron spin resonance in relation to absolute dating refer to and explain how it works:

Answer 25

Measures the properties of electrons in the crystals of minerals.

• Some common minerals collect electrons over time at a steady rate
• These trapped electrons are slightly magnetised
• As the amount of electrons increase, the amount of magnesium also increases (older sample)
• Useful for dating coral, mollusc shells and too enamel

Question 26

What is luminescence (Thermoluminescence and Optical Stimulated Luminescence) in relation to absolute dating and explain how it works:

Answer 26

Measure characteristics of minerals within sedimentary rock.

• When radiation strikes a mineral crystal, energy from the radiation can be trapped within the crystal and is released only when it is exposed to heat or light.
• In these techniques, the light emitted from a mineral is measured when it is heated or exposed to visible light.