Natural Selection, Speciation & Evolution

Question 1

evolution

Answer 1

Evolution is the change is species over time. It is usually very gradual, but in the correct circumstances, can be reasonably rapid.

Question 2

what does evolution lead to:

Answer 2

one species forming 2 (or more) new species
OR
a change in a species without the formation of a new species

Question 3

how does evolution occur

Answer 3

Evolution occurs in a species NOT in an individual

Question 4

it what two ways does evolution occur

Answer 4

convergent evolution
divergent evolution

Question 5

convergent evolution

Answer 5

(unrelated species become more similar)
occurs when different species
change in a very similar way
due to the species experiencing
the same selection pressures.

Question 6

divergent evolution

Answer 6

(one species changes into two species)
occurs when different adaptations occur (and are selected for) in separate populations of the same species. This normally occurs when the populations live in areas with different environments

Question 7

How do we know that evolution occurred?

Answer 7

a) we can see progressive change through fossils
b) many species have vestigial structures.

Question 8

what does Charles Darwin say about evolution

Answer 8

• proposed that evolution
  occurs through the process of
  Natural Selection.
• this theory relies on naturally
  occurring variation within
  populations that provides
  some of the organisms with a
  survival advantage.

Question 9

why is charles darwin important in this topic

Answer 9

his theory of evolution is most accepted

Question 10

what did his theory rely on and how was it veiwed?

Answer 10

• relied on favourable traits being inherited (his theory was
  formed long before knowledge of DNA/inheritence)
• was viewed as radically “anti-church”

Question 11

do adaptations occur because a species needs them, why?

Answer 11

It is important to realise that adaptations don’t occur because a species needs them. They arise through chance mutations and they help the individuals of that species survive.

Question 12

what is a reason that some species go extinct

Answer 12

Plenty of species have gone extinct though - largely due to the fact that the DNA didn’t mutate in a way that provided a benefit (or because the environment changed too quickly for the allele frequency for the beneficial adaptation to increase).

Question 13

Natural Selection

Answer 13

Natural Selection is a theory used to explain how the frequency of alleles changes within a popuation.

Question 14

what is needed for natural selection to occur

Answer 14

For natural selection to occur, there must be variation within the population. This variation occurs by chance through mutation which creates new alleles.

Question 15

what happens when an mutation gives an advantage in its habitat

Answer 15

If the mutation gives an organism an advantage in its habitat, it is more likely to survive, reproduce and pass the beneficial gene on to its offspring

Question 16

what happens when a trait continues to be beneficial

Answer 16

If the trait continues to be beneficial, its presence in the population will increase over generations

Question 17

what does the process of natural selection result in

Answer 17

The process of natural selection results in some individuals having more offspring than others.

Question 18

what is a selection agent + egs

Answer 18

The factor that acts on the population and favours some individuals more than others is known as the selection agent. It can include climate, predators, food availability or disease.

Question 19

how is Charles Darwins’ theory described

Answer 19

Although he did not come up with the phrase, the term “survival of the fittest” is often used to describe Charles’ Darwin’s theory of natural selection.

Question 20

what does the survival of the fittest phrase mean

Answer 20

The “fittest” organisms in this sense are the ones that are best adapted to their environment and are most likely to survive and reproduce

Question 21

why did Alfred Wallace receive no credit for the same theory?

Answer 21

Darwin was actually lucky to be credited
with this theory because Alfred Wallace
came up with the same theory at the
same time but Darwin’s book was
published first so he got all of the glory.

Question 22

what leads to the formation of a new species

Answer 22

an important process in evolution is speciation which can lead to the formation of a new species

Question 23

Whether two individuals are from the same species used to be determined by the following rule:

Answer 23

if they could breed together under natural conditions as produce a fertile offspring, then they are of the same species.

Question 24

how does DNA tell us if two individuals are the same species

Answer 24

Now they also use DNA to test whether two individuals are the same species. >1% difference is usually regarded as different species.

Question 25

speciation

Answer 25

Speciation is the process in which one species splits/diverges into 2 or more new species. It’s how new species appear in the fossil record.

Question 26

what are the three stages of speciation

Answer 26

It consists of 3 stages:
- variation - isolation - natural selection

Question 27

variation

Answer 27

must be present in the initial population or the subdivided populations as the process of speciation involves natural selection.

Question 28

isolation

Answer 28

the population must become geographically isolated so that gene flow can’t occur. The populations can become separated by the formation of rivers, dams, mountain ranges, deserts, clearings under power lines, car parks, salinity, soil pH etc.

Question 29

natural selection

Answer 29

Natural selection occurs independently in each population (with each having a different selection pressure).

Question 30

sub species

Answer 30

If the individuals in the 2 sub-populations look have evolved to look different but can still produce fertile offspring, they are called sub-species.

Question 31

new species

Answer 31

If they have evolved to look different and can no longer breed to produce fertile offspring, they are new species and reproductive isolation has occurred.

Question 32

can sub populations meet up again?

Answer 32

The 2 sub-populations may meet up again some time in the future

Question 33

Our species is called?

Answer 33

Our species is called Homo sapiens.

Question 34

did we evolve from monkeys or cavemen

Answer 34

we did NOT evolve from monkeys (although we do have a common ancestor)
- we did NOT evolve from cavemen

Question 35

phylogenetic trees

Answer 35

they are used to show which groups are most closely related

Question 36

who are the two closest living relatives of humans

Answer 36

two closest living
relatives are chimps and gorillas.

Question 37

primate

Answer 37

The order “primate” can be divided into several groups (each classified at the level of family)

Question 38

Hominoids:

Answer 38

Hominoids:
the most recently evolved group of primates (no tail)

Question 39

Hominins

Answer 39

The family Hominoid can be further divided and humans
belong to a group called Hominins.

Question 40

what is the main feature of Hominins and what structural changes occured for this?

Answer 40

The main feature of Hominins is that they are fully bipedal (walk on two legs). This involved structural changes to the pelvis and skull (where the spinal cord comes out changed position which allowed greater balance on two legs)

Question 41

Homo habilis

Answer 41

• handy man (evidence of tool use)
• larger brain (more protein in diet?)Homo

Question 42

Homo erectus

Answer 42

• used fire
• even larger brain (more protein in diet)
• evidence of care giving

Question 43

Homo sapien

Answer 43

• cultural evolution
• self-aware

Question 44

As species become more modern:
(slide 42)

Answer 44

• flatter face
• lower jaw shortens
• forehead less slanted/more vertical
• cranium capacity increases (which can hold a
  larger brain but that isn’t part of the skull)

Question 45

Homo neanderthalensis - How did that connection happen?

Answer 45

They lived at the same time as our species but are not our ancestors. Possiby through divergent evolution from Homo erectus.

Question 46

what does DNA say about neanderthals and our species

Answer 46

DNA evidence suggests that
breeding occurred between
neanderthals and our species but not
all offspring were fertile (so different species)