Genetics and Behaviour

Question 1

what did Darwin say about natural selection?

Answer 1

“Evolutionary change occurs as the heritable traits of successful individuals are spread throughout the population, whereas those traits of less successful individuals are lost.”
Darwin 1859

Question 2

example of natural selection

Answer 2

peppered moth variation depends on environment

Question 3

what happened to the human brain during evolution?

Answer 3

the human brain has increased in size during evolution
most of the increase in size occurred in the cerebrum
increased convolutions in the cerebrum have served to increase the volume of the cerebral cortex

Question 4

what mammals have the highest brain size to body weight ratio?

Answer 4

humans and tree shrew

Question 5

how much of the total body weight of humans and elephant makes up the brain?

Answer 5

the human brain makes up 2.3% of the total body weight
the elephant brain makes up 0.2% of it’s total body weight

Question 6

how much does the brain weigh at birth and how many neurones does it contain?

Answer 6

it weights an average of 350g containing about 100 billion neurons
production of new neurons almost ceases, except in the hippocampus and olfactory bulb but those that are already present grow and establish connections with each other

Question 7

how much does the adult brain weigh and when does it fully develop?

Answer 7

the human brain reaches its adult size of around 1400g and doesn’t develop until late adolescence

Question 8

how much DNA do humans share with chimpanzees, orangutans and gorillas?

Answer 8

chimpanzees and humans - 1.2%
orangutans and humans - 2.4%
gorillas and humans - 1.4%

Question 9

how did humans and chimpanzees lineages diverged?

Answer 9

humans and chimpanzee lineages diverged from a common ancestor about five to six million years ago

Question 10

which species played a significant part in human evolution and how?

Answer 10

the genus Homo was derived from Australopithecus (Southern Ape) at some time after three million years ago
the first hominid to leave Africa did so around 1.7 million years ago (Homo erectus)
Our own species, Homo sapiens, evolved in East Africa around 100,000 years ago

Question 11

explain Mendel’s theory

Answer 11

Austrian Monk bred true pea plants together
first generation: he crossed brown seeds and white seeds to produce all brown seeded peas because they all have one dominant brown seed allele and one recessive white seed allele
second generation: he crossed brown seeds with brown seeds to produce 75% brown seeds and 25% white seeds because 1 in 4 had 2 recessive alleles which became dominant

Question 12

define allele

Answer 12

two versions of the same gene
set of genes controlling a trait that sit at the same site of the chromosome

Question 13

define chromosome

Answer 13

strands of DNA

Question 14

define gene

Answer 14

a piece of DNA that directs protein synthesis

Question 15

define dominant allele

Answer 15

only one copy is required to express the trait

Question 16

define recessive allele

Answer 16

two copies are required to express the trait

Question 17

define genotype

Answer 17

genetic makeup of alleles

Question 18

define phenotype

Answer 18

observable trait from the combination of alleles

Question 19

define homozygous

Answer 19

when both alleles are the same e.g. BB or bb

Question 20

define heterozygous

Answer 20

when the alleles are different e.g. Bb

Question 21

what is DNA?

Answer 21

deoxyribonucleic acid, in the nucleus of each cell, contains the alleles
double helix structure
made of sugar phosphate backbone with nucleotide bases

Question 22

what are the nucleotides and which ones attach to each other?

Answer 22

adenine
thymine
guanine
cytosine
A <–> T
C <–> G

Question 23

what did Watson and Crick (1962) find?

Answer 23

they deciphered the DNA code
found that humans have 23 pairs of chromosomes

Question 24

explain the process of protein synthesis

Answer 24

1. the DNA molecule partially unravels exposing the structural gene that is to be expressed
2. transcription occurs: a strand of messenger RNA is transcribed from one of the exposed DNA strands and carries the genetic code from the nucleus into the cytoplasm of the cell
3. translation occurs: in the cytoplasm, the strand of messenger RNA attaches itself to a ribosome. the ribosome moves along the strand translating each successive codon into the appropriate amino acid, which is added to the lengthening protein by a molecule of transfer RNA
4. when the ribosome reaches the end of the messenger RNA strand, a codon instructs it to release the completed protein

Question 25

how do mutations occur?

Answer 25

transcription or translation errors

Question 26

define gametes

Answer 26

sex cells e.g. sperm cells, egg cells

Question 27

how are sperm cells created and the process

Answer 27

sperm cells are created by meiotic division 1. the fathers body cells have 23 pairs of chromosomes 2. the chromosomes duplicate themselves 3. the cell divides to create two cells each with 23 duplicated chromosomes 4. each cell divides again to create 4 sperm cells, each with 23 chromosomes, which is half the normal number

Question 28

how are egg cells created and the process

Answer 28

egg cells are created by meiotic division 1. the mother's body cells have 23 pairs of chromosomes 2. the chromosomes duplicate themselves 3. the cell divides to create 2 cells, each with 23 duplicated chromosomes, one of these cells dies 4. fertilisation occurs 5. the fertilised cell divides to create two cells, the cell without the sperm dies 6. the sperm and the egg combine to form a zygote with 23 pairs of chromosomes

Question 29

how does the zygote grow and the process

Answer 29

the zygote grows by mitotic division 1. the zygote has 23 pairs of chromosomes: half from the mother, half from the father 2. the chromosomes duplicate 3. the cell divides to create 2 cells each with 23 pairs of chromosomes 4. mitotic division occurs over and over until an adult organism is created

Question 30

explain the process of DNA replication

Answer 30

1. the two strands of the original DNA molecule unwind 2. the nucleotide bases on each strand attract free-floating complementary bases 3. two identical DNA molecules are created, each with one strand from the original DNA molecule and one new strand

Question 31

how many chromosomes do humans have?

Answer 31

humans have 23 pairs of chromosomes

Question 32

how many pairs of chromosomes determines gender? what are the chromosomes that females and males have?

Answer 32

gender is determined by 1 pair of chromosomes all females have XX chromosomes all males have XY chromosomes Y chromosome is smaller

Question 33

examples of sex-linked traits

Answer 33

colour blindness and haemophilia

Question 34

explain haemophilia

Answer 34

haemophilia is more prevalent in males than females dominant H = do not have haemophilia the gene for haemophilia is carried on the X but not Y chromosome females can be heterozygous or homozygous: HH, Hh, hh males can only have one gene: H, h

Question 35

disorders associated with single genes

Answer 35

down syndrome is caused by a chromosomal aberration resulting in an extra 21st chromosome single gene metabolic disorder Phenylketonuria (PKU)

Question 36

explain PKU disorder

Answer 36

discovered by a Norwegian Dentist called Asbjorn Folling PKU is transmitted by a recessive gene mutation on chromosome 12 cannot break down phenyalanine, amino acid common in food as a result build up in blood resulting in brain damage hospitals screen babies for high levels of this amino acid reduction of phenyalanine in diet relieves symptoms

Question 37

explain the Maze Bright Maze Dull study

Answer 37

Tryon (1934) Genetic control of cognitive ability Tryon ran a normal population of rats in a maze and separated out the ones that were really fast at learning the maze and ones that were really slow and allowed these two groups to breed separately. he then did the same with the two groups offspring. separating out the smart ones and breeding them and the dull ones and breeding them by the 8th generation the two groups behaviour in the maze was completely different. all of the animals in the bright group learnt the maze quickly and all of the animals in the dull group learnt it slowly

Question 38

explain the variation of the Maze Bright Maze Dull study

Answer 38

Cooper and Zubek found that the difference between the maze bright and maze dull rats was only seen if both groups were in impoverished environments. if the environment was enriched the impairment in the maze dull was removed demonstrating the importance of environment

Question 39

define dizygotic

Answer 39

from two eggs individually fertilised fraternal twins

Question 40

define monozygotic

Answer 40

from one egg split after fertilisation identical twins

Question 41

explain the Minnesota study of twins

Answer 41

Bouchard (1998) Twin studies twins reared apart showed that identical twins were more similar than fraternal twins on all psychological dimensions Turkheimer et al (2003) found heritability of IQ was near 0 in impoverished twins and near 1 (maximum) in affluent twins

Question 42

summary points

Answer 42

Mendel showed traits could have two variations, one dominant, one recessive. These codes for these traits are held in our DNA in groupings of nucleotide bases (genes) Half of our DNA is passed to our children Some disorders can be caused by the presence of a single recessive gene on a male X chromosome (Haemophilia) Some can be caused by mutations of single genes (PKU) Cognitive ability can not only be influenced by genes but also by the environment

Question 43

example of advantageous behavioural traits

Answer 43

older males attracted to younger females --> produce healthier offspring

Question 44

examples of advantageous behavioural traits in humans that might not appear advantageous

Answer 44

young females attracted to older males --> social dominance is adaptive --> dominant males produce more offspring than non-dominant males

Question 45

examples of advantageous behavioural traits in animals

Answer 45

some animals adopt other animals offspring --> doesn't change the survival chances of their own offspring much --> cost-benefit evolutionary pressure to take on imposter offspring --> overrides costs of mistakenly rejecting your own (Fisher, 2003) some animals cannot identify their own chick and adopt other ones --> better to have a healthy chick to give food to (Saino et al., 2000)

Question 46

define sentinel behaviour

Answer 46

looking out for predators and giving an alarm call is advantageous to the individual meaning that the animal will survive longer and have more offspring

Question 47

what do you get from risking your own life to protect others?

Answer 47

most behavioural biologists are skeptical about group-benefit group selection because if hereditary characteristics benefit a group but harm an individual's chances of reproducing, they will be eliminated over time no matter how good they are for the group all the altruistic ones that survived, it will be their genes that are passed onto the next generation sentinel behaviour - Clutton-Brock (1999)

Question 48

define altruistic behaviour

Answer 48

when animals behaviour benefits other individuals, even to the potential detriment of themselves

Question 49

what is direct fitness?

Answer 49

- sentinel behaviour in meerkats is adaptive as it leads to direct fitness which helps the individual - trait that will increase ability to survive and contribute large numbers of fertile offspring to the next generation - sentinel behaviour provides an advantage to the individual as it is the first to see the predator and so it is the first escape - it does not have a disadvantage in terms of stopping it feeding as the individual will only engage in the behaviour after it has finished feeding

Question 50

what is indirect fitness?

Answer 50

- alarm calling in Belding's ground squirrel - Sherman (1977) - making shrieking noises makes them more vulnerable to getting eaten - this is a big disadvantage however as they are surrounded by family they are more likely to be saved by those with similarities to them - by saving their family, more of their genetic material is passed on - trait increases ability to help kin survive and contribute large numbers of fertile offspring to the next generation - the animal making the alarm is most likely to get eaten so it does not benefit the individual but it does benefit others in the colony

Question 51

what evidence that this behaviour provides indirect fitness by saving kin?

Answer 51

only females make alarm calls other than direct offspring, males are not related to rest of colony so do not gain enough indirect fitness by saving others females are more likely to stay in the home area males more likely to spread to different colonies to increase genetic diversity only works if you recognise the kin

Question 52

how do you work out when there is enough benefit from indirect fitness from altruistic behaviour to evolve?

Answer 52

Hamilton (1964) the general evolution of social behaviour Hamilton's rule of altruistic behaviour would evolve if relatedness to recipient and benefit to the gene pool outweighs the cost R x b - c > 0 R = relatedness to recipient b = benefit to the gene pool of act c = cost of act

Question 53

how does kin selection work?

Answer 53

only works if you can recognise your kin Belding's ground squirrels are less aggressive and more altruistic to half siblings reared apart than to unrelated individuals reared apart Holmes (1986) animal behaviour

Question 54

kin selection in humans

Answer 54

Mothers can recognise photographs of their infants within 33hrs of birth and strangers can match photographs of mothers and infants, suggesting a physical resemblance among kin (Porter et al. 1984) Mothers can pick out their children's smelly t-shirts (Porter and Moore, 1981) Both mothers and fathers reliably recognise their infant's cries (Gustafsson et al, 2013)

Question 55

kin selection in swallows

Answer 55

Communal Bank swallows are able to identify their on kin which gives them an advantage on their genes are more likely to be passed on (Beecher, Beecher and Hahn, 1981) Solitary Tree swallows couldn't identify kin from calls but this skill is not needed as they don't come across other offspring as much (Leonard et al, 1997)

Question 56

extreme altruism

Answer 56

bringing up sisters instead of daughters Eusocial societies in Hymenoptra species e.g. bees, termites, wasps Bourke (1997) Kin selection in insects

Question 57

societies which exhibit extreme altruism:

Answer 57

1. cooperative care of brood 2. reproductive division of labour 3. overlapping adult generations

Question 58

explain extreme altruism in Hymenoptra species

Answer 58

Worker bees bringing up more and more generations that are not their own offspring. This occurs due to their genetic makeup: Females have 2 pairs of chromosomes - one from male and one from female - diploid - and are created from a fertilised egg Males have 1 pair of chromosomes - one from female - haploid - and are created from an unfertilised egg This means that sisters are share 75% of genes rather than 50% making them more related As a result, a female passes on more of their genes by helping to raise sisters than flying off and raising daughters

Question 59

extreme altruism in eusocial vertebrates

Answer 59

Naked mole-rats (Honeycutt, 1992) like bees they have a division of labour, queen largest and long-lived, other females do not breed unlike bees they are diploid and have no difference in physiology

Question 60

factors leading to eusocial society

Answer 60

inbreeding living in a contained nest harsh conditions outside of next

Question 61

benefits of extreme altruism

Answer 61

small genetic diversity leads to being more related to your sisters than offspring so acting to protect your brothers and sisters is more beneficial to your gene pool

Question 62

altruistic behaviour in non-eusocial vertebrates

Answer 62

- Emlen (1997) - Florida Scrub Jays help siblings as it will increase indirect fitness - 3/4 adult birds e.g. mother, father, brothers, sisters feeding 1 fledgling - Having helped out at the nest, they learn how to bring up the next generation which increases the likelihood that they can bring up their own fledglings - indirect and direct fitness