Module 4

Question 1

What is Biodiversity?

Answer 1

− variety in an ecosystem
− variety of habitats and variety of species

Question 2

Benefit of high species diversity?

Answer 2

− Stable ecosystem
− each species is less likely to become extinct (due to high genetic diversity)
− & if a species does become extinct it will not affect the food chain as there are other species available

Question 3

How to measure Species Diversity for an area?

Answer 3

− Species Diversity Index
− takes into account the number of different species and how many individuals there are for each species
− the larger the species diversity index, the larger the species diversity

Question 4

How does deforestation lower species diversity?

Answer 4

− (deforestation is the removal of trees for wood & space)
− decreases plant species diversity
− less variety of habitats
− less variety of food sources
− decreases animal species diversity

Question 5

How does agriculture/farming lower species diversity?

Answer 5

− deforestation to make space for farm
− only grow a few plants & keep a few animal species
− selectively breed plants & animals
− use pesticides to kill other species

Question 6

What is Classification?

Answer 6

placing organisms into groups

Question 7

What is Hierarchical Classification?

Answer 7

− large groups divided into smaller groups with no overlap
− domain, kingdom, phylum, class, order, family, genus, species

Question 8

What is Binomial Naming System?

Answer 8

− using Genus name and Species name to name organism
− Genus name first in capital, Species name second in lower case
− e.g. tiger = Felix tigris

Question 9

What is a Species?

Answer 9

​a group of individuals with similar characteristics that can interbreed to produce fertile ​offspring

Question 10

Why are the offspring from 2 different species mating infertile?

Answer 10

− offspring will have a odd number of chromosomes
− therefore, cannot perform meiosis, cannot produce gametes
− example: ​horse + donkey = mule,
​mule is infertile,
​horse has 64 chromosomes/donkey has 62 chromosomes,
​horse gamete has 32 chromosomes/donkey gamete has 31 chromosomes,
​therefore, mule has 63 chromosomes

Question 11

What is Phylogenetic Classification?

​

Answer 11

based on evolutionary relationships – how closely related different species are and how ​recent a common ancestor they have

Question 12

3 ways of comparing relationship between different species?

Answer 12

DNA Hybridisation: comparing DNA base sequence
​
​- take DNA from 2 species to be compared
​- radioactively label one of the DNA
​- heat both sets so double strand separates
​- cool so single strands join together
​- look for Hybrid DNA (one strand from species A, one strand from species B)
​- identify Hybrid DNA by 50% radioactivity
​- heat Hybrid DNA to measure similarity
​
​results =​higher temperature required
​more hydrogen bonds present
​more complementary base pairing
​more similar the base sequence
​more similar the species
​more closely related
​more recent a common ancestor

AA Sequence: comparing AA sequence for the same protein (e.g. haemoglobin in mammals)
​
​results = ​more similar the AA sequence
​more similar the DNA base sequence
​more similar the species
​more closely related
​more recent a common ancestor
​
​(comparing DNA sequence better then comparing AA sequence:
​DNA sequence provides information on INTRONS and triplet code is DEGENERATE)

Protein Shape:​ comparing shape of the same protein (e.g. albumin) using immunological technique

​- comparing species A and species B
​- take albumin from species A
​- place in a blood of rabbit
​- rabbit will make antibodies against albumin of species A
​- takes these antibodies and place in blood from species B
​- if the albumin in species B has a similar shape to species A,
​the antibodies will bind to form antigen-antibody complexes,
​this will then form a precipitate

​results = ​more precipitate
​more complexes
​more similar shape
​more similar the species
​more closely related
​more common recent ancestor

Question 13

What is Variation?

Answer 13

difference in characteristics between organisms

Question 14

Types of Variation?

​

Answer 14

intraspecific = differences between organisms of the same species
​interspecific = differences between organisms of different species

Question 15

Causes of Intraspecific Variation?

​

Answer 15

Genetic Factors = same genes but different alleles (allele are different type/forms of genes)

​Environmental Factors

Question 16

Causes of Interspecific Variation?

​

Answer 16

Genetic Factors = different genes and different alleles

​Environmental Factors

Question 17

Types of Characteristics?

Answer 17

Discontinuous and Continuous

Question 18

Properties of Discontinuous Characteristics?

​

Answer 18

characteristics fall into certain groups with no overlap (e.g. blood group) – determined by ​genetics only (a single gene)

Question 19

Properties of Continuous Characteristics?

​

Answer 19

characteristics show a range (e.g. height) – determined by genetics (a few genes, polygenes) ​and environment

Question 20

What is Genetic Diversity?

Answer 20

genetic variation, the variety of alleles within a population of a species

Question 21

Benefit of high genetic diversity?

Answer 21

species able to adapt with changes in the environment ​ e.g. if a new disease arises, some individuals will have characteristics to survive, and will reproduce passing on their alleles, so the species does not become extinct

Question 22

What can lower genetic diversity?

Answer 22

small population size (e.g. founder effect – where the numbers ​start low, or genetic bottleneck – where the numbers decrease)

Question 23

What is natural selection and adaptation?

Answer 23

− variation in population of species
(genetic diversity/genetic variation/variety in gene pool)
− new alleles arise by random mutation
− environment applies a selection pressure on the population
− those with favourable characteristics/favourable alleles/selection advantage/better adapted survive, the others die [natural selection]
− the ones that survive will reproduce, passing on their favourable alleles
− if this happens for many generations, then that characteristic will become most common – the allele will become more frequent [adaptation]

Question 24

What are the 2 types of selection?

Answer 24

stabilising and directional

Question 25

What is stabilising selection?

Answer 25

− when the environment favours those with the most common characteristic – those on the extreme dies out
− the common characteristic increases in proportion
− the range (standard deviation) will reduce

Question 26

What is directional selection?

Answer 26

− when the environment favours those individuals with characteristics on one of the extremes
− over time this will become the most common characteristic
− normal distribution will shift to that extreme

Question 27

What is a Gene?

Answer 27

− a section of DNA that codes for a protein
− made out of intron and exon
− intron = non-coding DNA (function e.g. turns gene on or off)
− exon = coding DNA (codes for protein)

Question 28

How does a Gene/Exon code for a Protein?

Answer 28

− made out of a sequence of bases
− each 3 bases code for 1 amino acid (called triplet code)
− therefore,
− sequence of bases
− determines sequence of triplet codes
− which determine the sequence of AAs
− = polypeptide chain/primary structure (folds to secondary, then to tertiary/quaternary)

Question 29

Properties of triplet code?

Answer 29

− degenerate = each AA has more than one triplet code
− non-overlapping = each base is read only once
− stop codes = occur at end of sequence – do not code for an AA

Question 30

How does a mutation lead to a non-functional enzyme?

Answer 30

− change in base sequence
− change in sequence of triplet codes
− change in sequence of AAs
− change in primary structure
− change in hydrogen/ionic/disulfide bonds
− change in tertiary structure (3D shape)
− change in active site shape
− substrate no longer complementary
− can no longer form enzyme-substrate complex

Question 31

How is a protein assembled?

Answer 31

− by transcription and translation
− transcription = production of a single stranded complementary copy of a gene (called ​ mRNA)
− translation = use sequence of codons on mRNA to assemble protein (tRNA brings in ​ AAs)
DNA vs RNA?

− deoxyribose sugar vs ribose sugar
− thymine vs uracil
− double stranded vs single stranded
− one type vs two types (mRNA and tRNA)

Question 32

What is mRNA?

Answer 32

− messenger RNA
− single stranded complementary copy of a gene
− carries the code for assembling protein (on DNA called triplet code, on mRNA called ​ codon)

Question 33

What is tRNA?

Answer 33

− transfer RNA
− single stranded RNA folded over into a ‘clover leaf’ shape (held by hydrogen bonds ​ between the bases)
− has an AA attachment site on the top
− has 3 specific bases on the bottom (anticodon)
− anticodon binds to complementary codons on mRNA

Question 34

What is Transciption?

Answer 34

− occurs in nucleolus of nucleus
− producing a single stranded complementary copy of a gene (called mRNA)
− DNA is double stranded, 1 strand called coding strand & 1 strand called template strand, the template strand will be used to build mRNA
− process,
− DNA Helicase breaks the hydrogen bonds between complementary bases in the gene
− the double strand of the gene unwinds
− leaves 2 separate strands (1 coding strand and 1 template strand)
− complementary RNA nucleotides bind to exposed bases on the template strand
− RNA Polymerase joins the sugar-phosphate backbone of the RNA strand
− leaves pre-mRNA (contains introns and exons)
− the copies of the introns are removed by splicing
− leaves mRNA

Question 35

What is Translation?

Answer 35

− takes place on ribosomes of Rough Endoplasmic Reticulum
− uses the sequence of codons on the mRNA to assemble the protein (tRNA brings in AAs)
− process,
− mRNA leaves nucleus via nuclear pore
− mRNA attaches to a ribosome
− complementary tRNA carrying specific AAs bind to the codons on mRNA via their anticodon
− the AAs on the tRNA are joined by peptide bonds

Question 36

What does Meiosis produce?

Answer 36

​4 genetically different cells, haploid (half the amount of chromosome/DNA)

Question 37

Benefits of Meiosis?

​

Answer 37

produces gametes which will be used in sexual reproduction in animals & plants
​(2 gametes fuse to form a zygote, zygote develops into organisms)

Question 38

Stages of Meiosis?

Answer 38

Interphase/Meiosis I/Meiosis II/Cytokinesis

Question 39

Interphase? ​

Answer 39

G1: protein synthesis
​S: DNA replication (doubles set of DNA)
​G2: organelle synthesis

Question 40

Meiosis I?

Answer 40

​Prophase I: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form, ​ ​ crossing over occurs
​Metaphase I: homologous pair of chromosomes line up in middle of cell and attach to ​ ​ spindle fibre via centromere
​Anaphase I: spindle fibres pull, homologous pair of chromosomes separate to opposite sides ​ by independent assortment
​Telophase I: chromosomes uncoil, nucleus reforms (left with 2 nuclei)

Question 41

Meiosis II?

​

Answer 41

Prophase II: DNA coils to form chromosomes, nucleus breaksdown, spindle fibres form
​Metaphase II: chromosomes line up in middle of cell and attach to spindle fibre via ​ ​centromere
​ Anaphase II: spindle fibres pull, centromere splits, sister chromatids move to opposite sides ​ by independent assortment
​Telophase II: chromatids uncoil, nucleus reforms (left with 4 genetically different nuclei)

Question 42

Cytokinesis?

Answer 42

separating cell into 4 (each receives a nucleus and organelles/cytoplasm)

Question 43

How does Meiosis produce Variation?

Answer 43

Crossing Over and Independent Assortment

Question 44

What is crossing over?

​

Answer 44

occurs in Prophase I of Meiosis I
​homologous pairs of chromosomes wrap around each other and swap equivalent sections of ​chromatids – produces new combination of alleles

Question 45

What is independent assortment?

Answer 45

​- in Anaphase I of Meiosis I – the homologous pairs of chromosomes separate
​- in Anaphase II of Meiosis II – the chromatids separate
​- independent assortment produces a mix of alleles from paternal and maternal ​ ​ ​ chromosomes in gamete

Question 46

What happens to DNA mass in meiosis?

Answer 46

quarters

Question 47

What happens to Chromosome number in meiosis?

Answer 47

halves (haploid)

Question 48

What is Mutation?

Answer 48

− Change in DNA
− 2 types: Chromosome Mutation and Gene Mutation

Question 49

What causes mutation?

Answer 49

random or due to mutagens (e.g. chemicals, radiation)

Question 50

What is a Chromosome Mutation?

Answer 50

− In plants, inherit more than one diploid set of chromosomes – called polyploidy
− In animals, homologous pair of chromosome do not separate in meiosis, so either inherit one extra or one less chromosome – called non-disjunction

Question 51

What is a Gene Mutation?

Answer 51

− a change in the base sequence of DNA
− 2 types = substitution and insertion/deletion
− substitution = replace one base for another, changes one triplet code
​can be silent (new triplet code codes for same AA), mis-sense (codes for a different ​AA, so protein shape changes slightly), non-sense (codes for a stop codon, so ​polypeptide chain not produced)
− insertion = adding a base, deletion = removing a base
​both insertion/deletion causes frameshift, all the triplet codes after the mutation ​changes, so normal polypeptide chain/protein not produced