Chapter 9,10,11 SAC:

Question 1

Mutation:

Answer 1

a permanent change to a DNA sequence

• For a mutation to be heritable, it must occur in a germline(sex) cell as this means it can be passed on to future generations

Question 2

Mutagens:

Answer 2

an agent that causes mutations in DNA

Question 3

Point Mutations:

Answer 3

a mutation that alters a single nucleotide in a DNA sequence

Question 4

Silent Point Mutation

Answer 4

a mutation in which a nucleotide is substituted for another nucleotide which results in a different codon that still codes for the same amino acid and therefore does not affect protein structure

Question 5

Missense Point Mutation

Answer 5

a mutation in which a nucleotide is substituted for another nucleotide resulting in a different codon which codes for a different amino acid and therefore affect protein structure

Question 6

Nonsense Point Mutation

Answer 6

a mutation in which a nucleotide is substituted for another nucleotide resulting in a stop codon, prematurely ceasing translation of the genes mRNA affecting protein structure.

Question 7

Frameshift Point Mutation

Answer 7

a mutation that involves the insertion or deletion of one or two nucleotides in a sequence, altering every codon from that point onwards, affecting protein structure

Question 8

Block Mutations:

Answer 8

a mutation that affects a large chunk of DNA or an entire gene

• These mutations usually occur during meiosis

Question 9

Deletion Block Mutation:

Answer 9

the removal of a section of DNA

Question 10

Duplication Block Mutation:

Answer 10

the replication of a section of DNA, lengthening the original strand of DNA

Question 11

Inversion Block Mutation

Answer 11

the reversal of a section of DNA

Question 12

Translocation Block Mutation:

Answer 12

the switching of two sections of DNA on different chromosomes

Question 13

Speciation:

Answer 13

the process by which populations genetically diverge until they become distinct species

Question 14

Allopatric Speciation:

Answer 14

the geographical separation of a population from a parent population resulting in the formation of a new species

• Relies on the presence of a geographical barrier

Question 15

Process of Allopatric Speciation:

Answer 15

1.Original population has variation in its genetic frequencies

2. A geographical barrier separates a population, preventing gene flow
   3. Different selection pressures act upon each population, favouring different phenotypes and allowing for genetic differences to accumulate
3. Eventually sufficient genetic differences accumulate so that the two populations can no longer interbreed to produce viable and fertile offspring

Question 16

Example of Allopatric Speciation:

Answer 16

• The Galapagos islands is a collection of 19 islands with 19 different ecological niches on each island(selection pressures and species) inhabited by Galapagos finches
  
  • Islands are also separated by the ocean which serves as a geographical barrier, preventing gene flow between them
  • As each different island has different food sources and selection pressures, different phenotypes(beak shape) are more advantageous, allow for genetic differences to accumulate and therefore for a new species to form

3 different species of Galapagos Finches:
Cactus Finch:
- Has a thin and elongated beak
- Primarily sources food from cacti using thin and elongated beak to prevent contact with spikes

Large-ground Finch:
- Thick and Short beak
- Primarily sources food from hard woody nuts with their thick and short beaks providing a significant amount of force to break open and extract the interior of woody nuts

Medium Ground Finches:
- Have moderate width and short beaks
- Primarily source their food from soft seeds

Question 17

Sympatric Speciation:

Answer 17

the divergence of a new species from an original species located in the same geographical area as a result of different selection pressures acting on different phenotypes

- Does not rely on the presence of a geographical barrier

• generally occurs in plants

Question 18

Example of Sympatric Speciation:

Answer 18

• The differences in soil pH on the Lord Howe Island is a major catalyst for the sympatric speciation between the Howea Forsteriana and Howea Belmoreana
  
  • Howea Belmoreana inhabits neutral and acidic soils(Low pH) whereas Howea forsteriana inhabits a region of alkaline soil(high pH)
  • The selection pressure of Howea Forsteriana inhabiting the alkaline soil resulted in the divergence of the sister species after the physiological differences began to develop, which after generations and generations, resulted in the formation of Howea Belmoreana

Question 19

Natural Selection:

Answer 19

a mechanism through which organisms that are better adapted to their environment have an increased chance of surviving and passing on their alleles

Question 20

4 Conditions of Natural Selection:

Answer 20

1. Variation: Individuals in a population vary genetically, which leads to phenotypic differences
   2. Selection Pressure: an environmental selection pressure impacts the survivability of organisms within a population and their ability to reproduce
   3. Selective Advantage: Individuals with phenotypes that are fitter or more advantageous under the environmental selection pressures are conferred a selective advantage, allowing them to survive and reproduce more successfully.
   4. Heritability: The advantageous trait must be heritable, allowing it to be passed on from the parents to their offspring. Therefore over time, the frequency of the advantageous allele will increase

Question 21

Selective Breeding/Artificial Selection:

Answer 21

the changing of a populations gene pool due to humans altering the breeding behaviour of animals and plants to develop a selected trait

- Can be used to select for the desirable trait but can also be used to select against an unwanted trait to remove it from a population

- Difference to natural selection is that NS involves a naturally occurring environmental selection pressure(predation, disease or climate change) which select individuals with a selective advantage within their environment

Question 22

Requirements for Selective Breeding:

Answer 22

• Variation: individuals in a population vary genetically, resulting in phenotypic differences
  • Selection Pressures: direct human intervention places an artificial selection pressure upon a population of individuals only allowing certain individuals with desirable traits to breed.
  • Heritability: the trait selected must be heritable, allowing it to be passed on from the parents to their offspring. Selected allele will increase in frequency

Question 23

Genetic Drift:

Answer 23

a random event that dramatically alters a population’s gene pool

• Reduces genetic diversity in a population through the random removal of alleles from the gene pool
• Smaller populations are more susceptible

Question 24

Bottleneck Effect:

Answer 24

a type of genetic drift which causes the reduction of genetic diversity that occurs when a large proportion of a population is removed due to a chance event

- They can dramatically reduce a population size and therefore allele frequencies

Question 25

Founder Effect:

Answer 25

the reduction in genetic diversity that occurs when a population is derived from a small unrepresentative sample of the original population

- E.g. If 10 green beetles left the original multicoloured population to form a new one, it would not mirror the initial gene pool and therefore the genetic diversity would be significantly lower than the original.

Question 26

Evidence of Interbreeding between Neanderthals and Homo Sapiens in the Middle East:

Answer 26

• Nuclear DNA analysis shows that 1-4% of non-African human DNA matches Neanderthals
  • Means that Neanderthals may have interbred with humans, as they left Africa, somewhere in the Middle East around 65 000ya and did not interbreed with african humans

Question 27

Evidence of Interbreeding between Neanderthals and Homo Sapiens in Siberia:

Answer 27

• 100 000yo DNA from Neanderthal fossils found in Siberia in 2016 contains a significant amount of ancient human DNA not found in other Neanderthal populations
  • This suggests a population of Neanderthals in Siberia may have interbred with an early form of humans around 100 000 years ago suggesting a second interbreeding event with humans.

Question 28

Evidence of Coexistence between Neanderthals and Homo Sapiens

Answer 28

• Neanderthals and Humans lived in the same regions around 100 000 - 40 000ya
  -20-30% of the Neanderthal genome is represented across the global population
  • This proves that H.sapiens and H. Neanderthalensis were able to coexist

Question 29

Evidence of Interbreeding between Neanderthals and Homo Sapiens due to MtDNA:

Answer 29

• No Neanderthal MtDNA is found in modern humans
• suggests that interbreeding was only successful between H.neanderthalensis males and H.sapien females

Question 30

Homo Neanderthalensis :

Answer 30

• Existed about 400,000 - 40,000 years ago
  
  • Lived in cold climates
  • Used fire and fine tools, ornaments, clothing and in some cases, buried the dead
  • Co-existed and interbred with H.sapiens
  • Evidence indicates a capacity for speech and possibly language
• Went extinct either due to being bred out by H.sapiens or by being killed by the H.sapiens

Question 31

Relative Dating:

Answer 31

a technique used to determine the relative age of a fossil by comparing its position to other fossils or rock in surrounding rock strata

- The age of a fossil can be determined by the age of the rock stratum in which it is found in

- Does not determine the exact age, just determines if this fossil is younger or older than another fossil

Question 32

Law of Succession/Statigraphy Principles:

Answer 32

• Sedimentary rock is formed by the accumulation of sedimentary layers on top of each other
  • The fossils closer to the surface must be younger than those that are found below them

Question 33

Geographical Timescales:

Answer 33

the aging of rock strata which allows us to determine that any fossils found within a strata belong a certain time period

Question 34

Index Fossil:

Answer 34

a group of widespread fossils which existed for a short period and have a known age

- Used as a reference to easily determine the age of unknown fossils

Question 35

Characteristics of an Index Fossils:

Answer 35

• Physically distinctive
  
  • Had a large population
  • Have existed in many geographical areas
  • Only lived within a known short period of time

Question 36

Transition Fossil:

Answer 36

a fossil that shows traits that are common to both its ancestral group and its descendent group

- Helps demonstrate evolutionary changes

Question 37

Characteristics of Hominins that changed over time and allowed for Bipedalism:

Answer 37

• Foranum magnum became more centrally located in humans allowing the head to rest on top of the spinal column providing balance while walking
  • Spine Curve: spine became more S shaped with a curve at the bottom and top to help vertical balance and walking
  • Rib cage: changed from funnel shaped to barrel shaped helping hominins maintain an upright posture for lengthy periods of time
  • Pelvis: became shallower and more bowl shaped which provides support for the upper body while standing and walking
  • Femur Angle: femur angle became larger allowing more weight to be distributed closer to the central axis giving more stability when walking
    • Foot: Humans big toe become more protruding and the other toes became more aligned due to the decreased need to grasp. The foot arch increased making bipedal locomotion more efficient and the heel size increased increasing bipedalism energy efficiency

Question 38

Bipedalism in Hominins leads to:

Answer 38

• Flexible and precise hands to complete tasks(hunting, cooking, carrying young)
  
  • Reaching for higher food
  • Cultural activities
  • Artistic activities
  • Viewing over grass to view predators and prey
  • Conservation of energy by walking on two limbs
  • Less surface area exposed to the sun gives them more time to forage/hunt

Question 39

Australopithecus Afarensis:

Answer 39

• Existed about 4mya and is the earliest known bipedal hominins
  
  • Human like pelvis and leg bones confirm they were bipedal
  • Were small in stature(1-1.5m) with a gracile build(slender) and were small brained(375-550cc)
  • Skull was similar to that of a chimpanzee with a flat nose, no chin, low forehead and a bony brow ridge
    
    • Had features indicative of primitive features normally associated with arboreal existence(locomotion of animals in trees)

Question 40

Australopithecus Africanus:

Answer 40

• Existed between 3.9-3mya
  
  • Was small in stature(1.1-1.4m), gracile and was bipedal

Differed to the Australopithecus Afarensis by:
- Having larger back teeth and smaller canines
- A parabolic jaw
- Being considered specific to South Africa

Question 41

Homo Floresiensis:

Answer 41

• Existed 95,000-13,000 ya
  • Equal in size to the smallest known australopithecines and has the brain size of a modern chimpanzee(400cc)
    • Scientists discovered despite their small brain, they used stone tools, fire and hunted dwarf elephants