5.1 Evidence for evolution

Question 1

When does evolution occur?

Answer 1

When heritable characteristics of a species change

Question 2

What is the difference between acquired characteristics and heritable chracteristics?

Answer 2

Acquired characteristics develop during the lifetime of an individual
Heritable characteristics are passed from parent to offspring

Question 3

What is the mechanism of evolution?

Answer 3

Natural selection

Question 4

What are the 3 types of evidence for evolution?

Answer 4

1. Fossil record
2. Selective breeding
3. Homologous structures

Question 5

How were geoogical eras named?

Answer 5

The sequence in which layers or strata of rock were deposited was worked out and the geological eras were named

Question 6

What did the strata of rock tell us?

Answer 6

The fossils found in the various layers were different - there was a sequence of fossils.

Question 7

What reliable method confirmed that various layers of rock were different.

Answer 7

Radioisotope dating revealed the ages of the rock strata and of the fossils in them.

Question 8

What is strata? What does it represent?

Answer 8

Layer of rock

Each strata represents a variable length of time that is classified according to a geological time scale (eons, eras, periods)

Question 9

What does the sequence in which fossils appear matches matches?

Answer 9

The sequence in which they would be expected to evolve

Question 10

What are some selection pressures (5)?

Answer 10

Disease, altitude, drought, predator, climate change

Question 11

What are the 4 stages of fossilization?

Answer 11

1. Death and decay - soft body parts are decomposed or scavenged, leaving only the heard body remains
2. Decomposition - The hard remains are rapidly covered with silt and sand, and over time more layers continue to build
3. Permineralisation - Pressure from the covering layers of dirt/rock cause the hard organic material to be replaced by minerals
4. Erosion/exposure - Movement of earth plates may displace the fossil and return it to the surface for discovery

Question 12

What are the conditions for fossils to form?

Answer 12

• Pressure - promote permineralisation
• Anoxic conditions - prevent decompositions by decomposers
• Hard body parts - soft body parts wont fossilise
• Body parts have to be preserved - protected against predators, damage etc
• Time

Question 13

What is a fossil record and what does it show?

Answer 13

Fossil record: The totality of fossils, both discovered and undiscovered

• The fossil record shows that over time changes have occurred in the features of living organisms (evolution)

Question 14

What is the law of fossil succession?

Answer 14

This chronological sequence of complexity by which characteristics appear to develop is known as the law of fossil succession

Question 15

Why is the fossil record so incomplete

Answer 15

• Very difficult for fossils to form because they require specific conditions
• May lie undiscovered
• May be disrupted e.g. predators, earthquakes, earth’s movement (movement of rock layers raise some parts but not some other parts) volcano etc.

Question 16

What is selective breeding/artificial selection?

Answer 16

repeatedly selecting for and breeding the individuals most suited to human uses.

Humans decide which traits are favourable as opposed to nature

Question 17

How does selective breeding/artificial selection provide evidence for evolution?

Answer 17

Provides evidence of evolution as targeted breading can show significant variation in a (relatively) short period
* Also shows that it is effective

Question 18

What does selection show but not prove?

Answer 18

Shows that selection can cause evolution but it does not prove that evolution of species has actually occurred natrually, or that the mechanism for evolution is natural selection

Question 19

What are homologous structures and analogous structures?

Answer 19

Homologous: A structure that appears superficially different (and may perform different functions) in different organisms, but has the same underlying structure

Analogous: Features adapted to perform the same function but have a different structure

Question 20

What does analogous and homologous structures provide evidence for?

Answer 20

Analogous structures provide evidence for convergent evolution

Homologous structures provide evidence for adaptive radiation

Question 21

What is convergent evolution and adaptive radiation?

Answer 21

Convergent evolution: Different origins and have become similar because they perform the same or a similar function

Adaptive radiation: Same origin, and they have become different because they perform different functions

Question 22

What are vestigial organs?

Answer 22

Reduced structures that serve no function

Question 23

How are vestigial organs explained by evolution?

Answer 23

These structures are easily explained by evolution as structures that no longer have a function and so are being gradually lost

Question 24

What does it mean when a two populations of the same species have undergone speciation?

Answer 24

They become so genetically different that they can no longer interbreed and produce fertile offspring. They have undergone speciation and formed two new species.

Question 25

What may cause speciation?

Answer 25

Geographic barrier

Question 26

What does an endemic species mean?

Answer 26

One that is found only in a certain geographical area

Question 27

What is industrial melanism?

Answer 27

the darkness—of the skin, feathers, or fur—acquired by a population of animals living in an industrial region where the environment is soot-darkened

Question 28

How does pollution affect peppered moths’ (Biston betularia) ability to camouflage pre and post industrial revolution?

Answer 28

• In an unpolluted environment, the trees are covered by a pale-coloured lichen, which provides camouflage for the lighter moth
• In a polluted environment, sulphur dioxide kills the lichen while soot blackens the bark, providing camouflage for the dark moth
• Before the industrial revolution, the environment was largely unpolluted and the lighter moth had a survival advantage
• Following the industrial revolution, the environment became heavily polluted, conferring a survival advantage to the darker moth