chapter eight: changes in species over time

Question 1

timeline showing the order in which the following groups evolved in

Answer 1

1. prokaryotic cells
2. photosynthetic organisms
3. multicellular organisms
4. plants
5. fish
6. amphibians
7. reptiles
8. dinosaurs
9. birds
10. mammals
11. insects
12. flowering plants
13. primates

Question 2

identify the conditions that favour fossilisation

Answer 2

• low oxygen levels
• low temperatures
• protected from scavengers

Question 3

explain how fossils can form

Answer 3

• an organism dies
• the organism is buried immediately (rapidly)
• protected from scavengers
• prevented from decomposition by low oxygen levels and low temperature
• over time, the molecules in the organisms are replaced by minerals from groundwater

Question 4

compare mineralised, mold, cast and trace fossils

Answer 4

mineralised fossils

• form when hard structures are replaced by minerals

mold fossils

• form when a petrified fossil dissolves and leaves an impression of the original
• these can be filled in to make cast fossils

cast fossils

• form when they are filled in molds

trace fossils

• form when traces of activity are buried before they are erased and turn into rock

Question 5

define the law of fossil succession

Answer 5

fossils are used to identify rocks of the same age - fossils found in the same layer as rock formed at the same time

• different kinds of organisms do not occur randomly in the fossil records but are found only in rocks particular ages and appear in a consistent order

based on the law of fossil succession (older fossils are in lower rock)

Question 6

describe the features needed for a species to be used as index fossils

Answer 6

index fossils must be

• abundant
• distributed worldwide
• existed for only a short period of time
• found in restricted depths of rock strata

Question 7

how are index fossils used in relative dating

Answer 7

index fossils can be used to determine the relative ages of rock strata anywhere in the world

• index fossils are of organisms that were common throughout the world for a limited geological time

Question 8

describe the importance of transitional fossils such as archaeopteryx in identifying the timeline of evolution

Answer 8

transitional fossils can tell us about major changes - evidence of evolution

• transitional fossils remains of a life form that exhibits traits common to both an ancestral group and its derived descendants group
• e.g. archaeopteryx shows characteristics presence of feathers and a wishbone, however it also showed some reptilian features not lost in modern birds. (they were also not capable of the magnificent flight of modern birds)

Question 9

describe how the law of fossil succession allows relatives dating to occur

Answer 9

older fossils have to be below younger fossils within the strata

• if you find a fossil below, it must be older

Question 10

describe how co-paring the ratio of carbon-14 to carbon-12 can indicate the time an organism died

Answer 10

the more carbon-12 in an organism, the more time has passed since the organism has died

• the more half-lives there are, the more time has passed (each substance has a different half-life time)

Question 11

define half life

Answer 11

the time taken for the radioactivity of a specified isotope to fall to half its original value.

Question 12

define species

Answer 12

a group of organisms that can reproduce with each other in nature and can produce fertile offspring (exchanging genes)

Question 13

describe the process of allopatric speciation (include gene flow)

Answer 13

allopatric speciation is when populations are geographically seperate

1. populations are geographically separated by a physical barrier

• there is no gene flow between populations, resulting in the populations to begin to experience genetic divergence such as through mutation

2. over many generations, the isolated populations are subjected to different environmental selection pressures, which leads to different phenotypes being selected for by natural selection or genetic drift

• may evolve to become so different that if individuals from the daughter population meet they would no longer mate or produce fertile offspring

3. now there are two distinct gene pools and different species

Question 14

give examples of isolating mechanisms

Answer 14

isolation mechanisms: something that stops one species from breeding with each other

• geographical barriers (mountains or different environment)
• temporal isolation (different mating seasons)
• mechanism isolation (things that prevent a species from breeding with another)

Question 15

describe how the Galapagos finches diverged into 13 seperate species

Answer 15

• Galapagos islands have variety of habitats - arid regions and mountainous regions
• differing environmental selection pressures on each of the islands based on food availability (main environmental pressures) resulted in change in the beak space due to the different food source and diet
• after the finches had arrived on an island they become geographically isolated due to the surrounding ocean hence over time allopatric speciation occurs
• their beak shape evolved rapidly by allopatric speciation

Question 16

what is sympatric speciation

Answer 16

speciation without the presence of a geographic barrier where different species arises within the same population

• new species arise without a physical barrier
• both species share the same ancestor
• they are both found/evolve in the same location from a common ancestor but are considered different
• PRE-ZYGOTIC ISOLATION - THEY CANNOT MATE

Question 17

describe the process of sympatric speciation

Answer 17

• the initial population has variation
• Then there is a change that starts to separate the time of breeding
• over time, that becomes bigger so that it is a discrete breeding time between both groups

Question 18

explain why sympatric speciations are rare

Answer 18

• it doesn’t happen very often
• It is not likely that groups living closely together will evolve differently from each other
• gene flow can still occur
• genetic drift has less of an impact
• less likely to be isolated

Question 19

summarise the events that led to different species of Howes palms in the same area

Answer 19

• both species of Howes palms share the same ancestor
• both found in the same location from a common ancestor
• barrier resulting from the dirt they grow in
• the soil leads the plants to flower at different time
• over time, flowering times changed to have no overlap therefore they cannot reproduce

Question 20

what evidence is there for evolution?

Answer 20

• fossils
• biogeographic distribution
• comparative (anatomy, embryology, DNA)

Question 21

define speciation

Answer 21

the process of new species arising/the formation of a new species

Question 22

process of speciation

Answer 22

1. population has variation
2. populations are isolated/is split by a physical/geological barrier, by preventing gene flow
3. different conditions (selection pressures) occurs on each side
4. different adaptations arises one each population
5. they are now different species and cannot breed

Question 23

what evidence do vestigial structure provide for evolution

Answer 23

• they indicate the relatedness between species
• the structure are similar, indicating that species share and have evolved over time from a common ancestor, however, the structures were once functional in the ancestors

Question 24

what is a common ancestor

Answer 24

• is a species that existed earlier in the fossil record
• evolved into two or more different species
• an ancestor shared by later species