TOE/NS 10

Question 1

What is a fossil?

Answer 1

Any evidence of living things from the distant past

Question 2

Outline the different types of fossils

Answer 2

• Original fossil → parts of original organism
• Indirect fossil → an imprint or cast of the organism
• Replacement fossil → mineral chemicals have gradually replaced the organism
• Carbon film fossil → organism has decomposed to leave a black carbon silhouette in rock

Question 3

When do fossils form?

Answer 3

When dead organisms are not eaten by scavengers and are quickly covered to prevent decomposition by microorganisms or reaction with oxygen

Question 4

Where are fossils found?

Answer 4

Sedimentary rock

Question 5

In what environments do fossils tend to form?

Answer 5

• riverbed, seabed, lakebed
• swamps
• special cases - amber, tar pits, deserts, ice

Question 6

Why do fossils give a limited, biased view of life from the past?

Answer 6

• most fossils are found underneath water → not all creatures were water-dwelling
• hard parts of organisms (e.g. bones, shells) are harder to break down and tend to be preserved → we rarely have fossils of soft animals such as slugs or jellyfish

Question 7

How does relative dating work?

Answer 7

uses comparison of fossils to find out if one is older/younger than the other

Question 8

What are two methods of relative dating?

Answer 8

• Steno’s law of superposition is used to compare fossils from one location → states that oldest layers are at the bottom and youngest layers are at the top
• Index fossils are fossils used to compare the age of fossils at different locations → index fossils must be easy to identify, abundant, found in many locations, and present for only a short period of time (e.g. trilobite and ammonite)

Question 9

What is absolute dating?

Answer 9

A technique used to determine the actual age of the fossil (not 100% accurate)

Question 10

What is one form of absolute dating?

Answer 10

Radioactive dating

Question 11

How does radioactive dating work?

Answer 11

• analyses presence of radioisotopes and the stable element it decays to
• percentage that has decayed is calculated
• percentage decayed can be used to determine the age using half-life

Question 12

What is half-life?

Answer 12

The time is takes for half the radioisotopes to decay

Question 13

What is a radioisotope?

Answer 13

A radioactive unstable element that loses parts of it’s nucleus to become stable

Question 14

What does the fossil record show?

Answer 14

• not all organisms that have existed still survive today
• different organisms have been dominant at different periods of time in the Earth’s history, and then disappeared

Question 15

What is the fossil record?

Answer 15

When all fossils are placed in order from oldest to youngest

Question 16

What is the geological time scale?

Answer 16

When the history of life on Earth is marked into different time periods according to when species appeared & disappeared

Question 17

What is an adaptation?

Answer 17

a characteristic of an organism that allows it to survive in its environment

Question 18

What are the classifications of adaptations?

Answer 18

• structural - a physical structure e.g. webbed feet
• behavioural - a behaviour e.g. huddling to keep warm
• physiological - an internal process/mechanism e.g. heart rate slows when swimming

Question 19

What is the relationship between a species having a wide variety of genes and it’s ability to survive?

Answer 19

a wide variety of genes will have a wide variety of characteristics, meaning that the species is more likely to survive in a changing environment

Question 20

Who came up with the theory of evolution by natural selection?

Answer 20

Charles Darwin and Alfred Wallace (separately)

Question 21

What is the theory of evolution by natural selection?

Answer 21

• When there is a change in an environment, some characteristics allow members of a species to survive better because they suit the particular environment
• Members who survive are more likely to reproduce & pass on their adaptations
• Over successive generations, more members of the species show the same adaptations

Question 22

What did Darwin notice about finches?

Answer 22

• vegetarian finches have a heavy beak to pull buds from plants
• tree finches have grasping beaks to eat grubs & insects
• ground finches have crushing beaks to eat seeds and cactus
• finches on the Galapagos islands (off the coast of Ecuador) were most similar to finches in South America

Question 23

What is a selection pressure?

Answer 23

a change in an environment

Question 24

What is biogeography?

Answer 24

the study of the geographical distribution of living things, both in the present and the past. It shows that a species is similar to species in an adjacent region.

Question 25

What does the fossil record of the horse show?

Answer 25

It shows a gradual change in the size of the horse from small to large due to changes in its environment over 60mil years

Question 26

What is a transition fossil?

Answer 26

a fossil that suggests a sudden change from one group of organisms to a significantly different group

Question 27

What is an example of a transition fossil?

Answer 27

Archaeopteryx:
* skull shape with teeth & long bony tail (reptile)
* wings and feathers (bird)

Question 28

What is comparative anatomy?

Answer 28

the comparison of structures in different living things, looking for similarities

Question 29

What is an example of comparative anatomy?

Answer 29

humans, monkeys, frogs, lizards, bats, cats and whales all have five digits at the end of their forelimbs, this is called a pentadactyl limb

Question 30

What is molecular biology?

Answer 30

the study of chemicals used by cells & the processes in which they are used

Question 31

How does molecular biology relate to TOE/NS?

Answer 31

• all living things contain DNA
• all living things rely on proteins to control chemical reactions
• all living things possess the same cell membrane structure
• proteins that serve the same function in different organisms have a very similar amino acid sequence (~90% are the same)
• DNA is made of the same components joined in the same way in every species