Speciation, fossilisation and relatedness

Question 1

Speciation

Answer 1

is the process by which populations genetically diverge until they become different species

Question 2

Species

Answer 2

are a group of individuals who are able to breed with each other and produce viable and fertile offspring

Question 3

viable

Answer 3

able to survive

Question 4

fertile

Answer 4

the ability to reproduce

Question 5

Allopatric speciation

Answer 5

the geographic separation of a population from a parent population resulting in evolution of a new species

Question 6

geographic barrier

Answer 6

a physical barrier that isolates populations from each other, preventing gene flow and allowing genetic differences to accumulate

Question 7

The process of allopatric speciation

Answer 7

1. initially a population(s) of the same species becomes seperated by a geographical barrier preventing gene flow
2. the isolated populations are exposed to different selective pressures, favouring different phenotypes and allowing genetic differences to accumulate
3. over time, sufficent genetic differences accumulate in the two population as they can no longer interbreed to produce viable, fertile offspring. Hence, two species are formed.

Question 8

Allopatric speciation

Answer 8

the geographic separation of a population of a population from a parent population resulting in the evolution of a new species

Question 9

geographic barrier

Answer 9

a physical barrier that isolates populations from each other, preventing gene flow and allowing genetic differences to accumulate

Question 10

Fossil record

Answer 10

information from fossils arranged in chronological order helping to map the history of life on Earth, placing species in the appropriate geological time frame

Question 11

fossils

Answer 11

are the preserved remains of long-dead organisms

Question 12

Process of fossilization

Answer 12

1. usually begins when remnants of an organism are rapidly covered by sediment.
2. Over time, layers of sediment upon each other and pressure pushes these layers together forming sedimentary rock
3. When devoid of oxygen, microorganism and other disturbances the remains are preserved

Question 13

Conditions that contribute to fossilisation

Answer 13

areas of rapid sediment accumilation
physical protection from scavengers and decomposers (eg fungi and bacteria)

Question 14

Permineralised fossils

Answer 14

fossil formed when organic matter is gradually replaced by hard minerals

Question 15

Impression fossils

Answer 15

fossils formed when an organism is encased in material but decompose or is removed and the gap is filled with another substance. Also known as cast and mould fossils

Question 16

Trace fossils

Answer 16

fossils of objects or structures indicating the presence of organisms, rather than the organisms themselves ( nests, eggs, footprints)

Question 17

Mummified fossils

Answer 17

fossil formed when the body is under conditions that slow down or stop the decaying process
found trapped in caves, ice and in dry caves

Question 18

Absolute dating

Answer 18

works out the absolute age of the fossil in years
eg. radiometric dating

Question 19

Relative dating

Answer 19

age of fossil determined by relative dating techniques
Describes the age of a fossil compared to other fossils, instead of a fossil’s age in years
Relies on strata which are separate layers within sedimentary rock
fossil succession is the principle that fossils of the same age will be in the same layer of sedimentary rock, and fossils found in a higher or lower sedimentary layer will be younger or older respectively. Also known as the law of superposition

Question 20

transitional fossils

Answer 20

fossils that show an intermediate stage of evolution

Question 21

Relatedness between species

Answer 21

Evolutionary studies provide evidence that all of life on Earth is related.
Relatedness between species can be shown through similar morphology (physical structures) and shared DNA sequences.
This evidence suggests that related species evolved from a common ancestor in the past.
The more similar the structures or DNA sequences, the more recently the two species diverged from a common ancestor.
These theoretical relationships are often illustrated using phylogenetic trees.

Question 22

Structure of phylogenetic trees

Answer 22

Phylogenetic trees usually have a line at the base called the root representing the common ancestor.
Each line on the tree is called a branch.
These branches split away from each other at nodes, which represent a divergence between those two taxa.
The end of a branch is called the leaf. This is where the present–day or extinct species are found, labelled with the species or taxa name