Module 4 - OCR A Level Biology

4.1.3 CLASSIFICATION AND EVOLUTION

4.1.3 CLASSIFICATION AND EVOLUTION

Order of taxonomic groups

Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species

What is the biggest taxonomic group?

Kingdom

What are the three domains?

Archaea, bacteria and eukarya

why is classification used?

• identify species

• predict characteristics

• find evolutionary links

• same system for all scientists

What is the definition of a species?

A group able to reproduce to produce fertile young

If two different species breed, why isn't their offspring fertile?

• their offspring will have an odd number of chromosomes

• meiosis + gamete production cannot take place bc all chromosomes have to line up

What is the binomial system?

advantage?

1st word = genus 2nd word = species

genus always capitalised

italics/underline whole name

advantage: scientists from all over the world can use the same system

What is genus does the "Ambystoma mexicanum" belong to?

Ambystoma

What species does the "Capra aegagrus" belong to?

Aegagrus

what are the 2 classification systems?

classic 5 kingdom

3 domain system with 6 kingdoms

what are the 5 kingdoms?

Prokaryotae

Protoctista Fungi Plantae Animalia

• multi-cellular

• membrane-bound organelles

• heterotrophic feeders

Animal kingdom

• unicellular

• no membrane-bound organelles

Prokaryote kingdom

e.g bacteria

• unicellular

• membrane-bound organelles

• autotrophic/heterotrophic/parasitic

Protoctista kingdom

Which kingdom does an amoeba belong to?

Protoctista kingdom

• multicellular

• membrane bound organelles

• autotrophic feeders

• contain chlorophyll

Plant Kingdom

• unicellular/multicellular

• membrane-bound organelles

• saprophytic feeders

Fungi Kingdom

also have cell wall made of chitin

e.g yeast

How does domain system work?

grouped by rRNA

Eukarya = 80s ribosomes Archaea = 70s ribosomes Bacteria = 70s ribosomes

How many kingdoms are in the Eurkaya domain?

4

Which kingdom is split in half by the bacteria and archaea domain?

Prokaryotae into Eubacteria and Archae-bacteria

what is phylogeny?

evolutionary relationships between organisms

reveal which group an organism is related to and how closely related

study = phylogenetics

what is a phylogenetic tree?

represents evolutionary relationships

show how diff. species evolved from one common ancestor

closer the branches of the tree, closer the evolutionary relationship

groups which share their own common ancestor = sister groups e.g A/B and E/F

how do classification and phylogeny work together?

advantages of phylogeny

classification uses knowledge of phylogeny to confirm that how an organism has been classified is correct

advantages:

• Phylogeny produces a continuous tree so not forced to put into a specific group where organism doesn't fit

• easier to compare

What was Darwin's Theory of Evolution?

Natural selection

what is the evidence for evolution (natural selection)?

• palaeontology (study of fossils)

• comparative anatomy

• comparative biochemistry

How does comparative biochemistry show evidence for evolution?

CB looks at the dif proteins/molecules in diff organisms

some molecules are highly conserved (hardly change) among species e.g cytochrome C, rRNA

slight changes can identify evolutionary links

species with similar DNA + proteins = more closely related

What evidence do fossils provide for evolution?

• fossils of simplest organisms are found in oldest rock layers while more complex vertebrate organisms found in more recent rocks

• sequence in which animals are found e.g plants before animals

• similarity in anatomy of fossil organisms to today's organisms suggest evolutionary relationships

• however not complete as soft-bodied organisms completely decay

interspecific variation

variation among members of different species

e.g bird has feathers and dog has fur

intraspecific variation

differences between organisms within a species

e.g people vary in height + colour

What are the two causes of variation?

Genes and environment

What are the three major causes of genetic variation?

Alleles

• individuals in a species may inherit different alleles

mutations

• changes to DNA changes the proteins coded for

• if mutation occurs in gametes too, can be passed down to offspring

meiosis

• independent assortment

• crossing over

sexual reproduction

• different from parent

How are plants more affected by the environment?

Plants can't move whereas animals can move to find food and shelter

example of environmental variation

Hydrangeas produce blue flowers in acidic soil and pink flowers in alkaline soil

difference between discontinuous and continuous variation?

discontinuous variation can only result in certain discrete individual categories. controlled by 1 gene

for continuous variation the values are within a range. controlled by multiple genes + influenced by environmental factors

examples of discontinuous variation?

Blood groups eye colour gender shape of bacteria

use bar chart

examples of continuous variation?

Height mass

What is standard deviation a measure of?

How spread out the data is

Greater the standard deviation the greater the spread of data

in terms of variation, a characteristic which has a high standard deviation has a large amount of variation

What is the formula for standard deviation?

x̄ = mean value

Σ = the sum of

x = value measured

n = total no. of values in the sample

normal distribution curve

the bell-shaped curve that results from plotting continuous variation data on a graph (usually)

50% values are greater than the mean and 50% below

most values close to the mean

bell-shape symmetrical around the mean

What does the student's t test compare?

Means of two sets of data

see whether there's a significant difference

requirements for t-test

data must be normally distributed

enough data to calculate reliable mean

diff sample sizes can be used

What is the equation for the student's t test?

x̄1 = mean of population 1

x̄2 = mean of population 2

S1 = standard deviation of population 1

S2 = standard deviation of population 2

n1 = total number of values in sample 1

n2 = total number of values in sample 2

what do you do with value calculated in t-test?

then must calculate degrees of freedom using this equation: df = (n1 + n2) - 2

compare df value with table

if your t-test value is lower than the value at 5% then you have to accept the null hypothesis because you can't be more than 95% confident that the results are due to chance

e.g if df=18 for test value of 2.07, have to accept the null hypothesis bc 2.07 < 2.10

*basically the higher the t-test value for a particular df, the more likely it is to be significant

What is a null hypothesis?

null hypothesis states that two variables are not related and any observed difference would be due to chance.

e.g There will be no significant difference in/of ....... compared with .......

MUST accept or reject null hypothesis

What does Spearman's rank correlation coefficient look for?

Relationships between data sets

whether they are correlated (negative correlation, positive correlation, no correlation)

How is the correlation coefficient calculated (for Spearman's rank)?

rs = correlation coefficient

d = difference in ranks

Σ = sum of

n = no. of pairs of data

How do you work out the strength of correlation from a Spearman's rank?

might have to calculate df

OR

n = no. of pairs of data, find correct n row in table, go along to p=0.05 value, and compare rs value to p = 0.05 value

if rs is higher than p=0.005 value then only 5% chance the correlation was by chance i.e 95% confident that correlation was not due to chance

e.g if rs = 0.6500 when n=10, less than 5% that correlation was due to chance, however not less than 2% that correlation was down to chance

what is an adaptation?

characteristics that increase an organism's chance of survival and reproduction

What are the three types of adaptation?

Anatomical

• physical features internal + external

behavioural

• the way an organism acts

physiological

• processes that take place inside an organism

examples of anatomical adaptations

Body covering

• e.g feathers help bird to fly, fur helps bears stay warm, waxy cuticle, spikes to deter hebivores

camouflage

• harder for predators to spot it

teeth

• for diet e.g sharp teeth for meat, continuously growing teeth for tough plants

mimicry

• fool predators into thinking its harmful

examples of behavioral adaptations

survival e.g playing dead

courtship e.g dance

• increases chance of reproduction

migration

• get better food, climate

hibernation

• save energy

examples of physiological adaptations

poison production

antibiotic production

water-holding (e.g cacti, camel)

reflexes

temperature regulation

what are analogous structures?

structures that have evolved differently on different species for the same function

e.g tails on whales and fish perform same role but diff. structures

What is the term for when unrelated species share similar traits?

Convergent evolution

example of convergent evolution

marsupial mole and placental moles

similar because they have adapted to similar climates and food supplies

different reproduction methods reflect that they are still different

CHECK WITH CGP BOOK

what are selection pressures?

factors that affect the organisms chance of survival or reproductive success

e.g predation, competition for mates & resources, disease

natural selection process

1. organisms within a species show variation in characteristics due to different genes

2. organisms whose characteristics are best adapted to selection pressures have an increased chance of survival and successful reproduction (less well-adapted species die)

3. successful organisms pass the allele with the advantageous characteristic onto their offspring (organisms w/o aa less likely to successfully pass it on)

4. repeated for every generation and over time the proportion of individuals with the advantageous adaption increases. Frequency of the allele that codes for particular characteristic increases in populations gene pool.

5. over long time can lead to evolution of new species

How to answer question on why a particular characteristic increases in a population

• identify adaptation

• explain how it helps organism survive and reproduce

• state this organism passes on allele with advantageous characteristic

• state how this increases the alleles frequency in the population

4.1.3 CLASSIFICATION AND EVOLUTION

4.1.3 CLASSIFICATION AND EVOLUTION

4.1.2 BIODIVERSITY

4.1.2 BIODIVERSITY

What are the three levels at which biodiversity can be studied?

Habitat, species and genetic

what is a habitat?

where an organism lives

e.g woodland, stream

What is species richness?

The number of different species in an area

What is species evenness?

A comparison between the numbers of each different species in an area

what is genetic biodiversity?

Variety of genes that make up a species leading to different characteristics

e.g diff breeds in a species

what are the two types of sampling?

random and non-random

Random sampling

selecting individuals by chance

random generation of co-ordinates

Three types of non-random sampling

opportunistic

stratified

systematic

Which method of sampling is weakest?

Opportunistic

least likely to be representative

Which method of sampling uses organisms that are conveniently available?

Opportunistic

Which method of sampling divides a population into sub-groups and takes proportional samples?

Stratified

subgroups (strata) of a given population are each adequately represented within the whole sample population e.g male and female

Which method of sampling uses a transect line?

Systematic

transect = marking a line and taking samples at specified points

why isn't a sample fully representative?

how can you reduce this effect

sampling bias

• use random sampling

chance

• use a large sample size

Which method of sampling best reduces bias?

Random

Pooter

used to catch small insects

sweep nets

used to catch insects in areas of long grass

Pitfall traps

used to catch small invertebrates such as beetles, spiders and slugs

tree beating

Hitting the branches of a tree and collecting small animals that fall out on white sheet

collect small invertebrates

kick sampling

used for organisms in a river

river bank/bed is kicked to disturb the substrate

net is held downstream to capture organisms released into flowing water

What is measured using an anemometer?

Wind speed

ms-1

how is light intensity measured?

light meter

units = lux

What is used to sample plants?

Quadrats

two types of quadrat

how to measure species richness

all above techniques e.g quadrats, pooters etc

how to measure species evenness

count total amount of different organisms

then calculate how many diff species present

e.g 10 total organisms:

• if 9 aphids found and 1 ant this is less even then 2 ants, 3 aphids and 5 spiders

3 ways calculate number of species in a quadrat

frequency - count number of squares where the species present

percentage cover

Capture-mark-release-recapture

used for estimating population size

• lots of individuals of a species captured

• organisms marked and released

Another sample of individuals captured

By comparing the no. of marked individuals with the number of unmarked individuals in 2nd sample, can estimate population size.

What is the formula of Simpson's index of biodiversity?

N = total number of organisms of all species

n = the total number of organisms of a particular species

what does it mean when the Simpson's index of biodiversity is closer to 1?

closer to 1 = more diverse

closer to 0 = less diverse

higher the value the more diverse the habitat

What is monoculture?

Planting only a single species of crop

low biodiversity

how is genetic biodiversity created?

differences in alleles among individuals of a species

more alleles present, more genetically biodiverse

why are species with greater genetic biodiversity less likely to go extinct?

• more likely to adapt to changes in the environment

• bc more likely there are organisms within the population that have an advantageous allele

What can increase genetic biodiversity?

possible no. of alleles in population must increase

• mutations in the DNA to create a new allele

• interbreeding between different populations - alleles transferred

What can decrease genetic biodiversity?

possible no. of alleles in population must decrease

• selective breeding (artificial selection) e.g pedigree animals

• captive breeding programmes → small no. of individuals available to breed

• artificial cloning

• natural selection → species evolve w/o advantageous alleles die out

• genetic bottlenecks → few individuals survive an event and only alleles of surviving members available to pass onto offspring

• founder effect → small no. of individuals create a new colony

• genetic drift → random nature of alleles being passed on means frequency of occurrence of an allele will vary, can lose alleles

How to measure genetic biodiversity?

• measure polymorphic genes (genes w/ more than 1 allele)

• greater the no. of polymorphic genes, greater the genetic biodiversity

factors affecting biodiversity

deforestation

agriculture

climate change (burning fuel leads global warming)

how does deforestation affect biodiversity?

• reduces no. of trees present

• species diversity reduced

• destroys habitats

how does agriculture affect biodiversity?

• deforestation

• remove hedgerow habitat

• pesticides and herbicides

• monocultures - only a few animal species supported by 1 plant

What are the three major reasons for conserving biodiversity for humans?

Aesthetic, economical and ecological