4.3 classification and evolution

define classification

the process of naming and arranging organisms into groups based on their characteristics

name the groups in the classification system

domain

kingdom

phylum

class

order

family

genus

species

what are the two components to a binomial name?

generic name = the genus that the organism belongs to, two closely related species will share the same genus

specific name = the species that the organism belongs to

what is the advantage of the binomial naming system?

it is universal; an organism’s binomial name is the same everywhere in the world

name the five kingdoms and the three domains

kingdoms: prokaryotae, protoctista, fungi, plantae, animalia

domains: bacteria, archaea, eukaryota

how was the domain system of classification developed?

by analysing molecular differences between organisms to determine their evolutionary relationships (phylogeny)

what is the difference between classification and phylogeny?

classification is simply sorting organisms into groups

phylogeny investigates the evolutionary relationships between organisms

explain how natural selection results in evolution?

• random mutations result in new alleles

• some alleles provide an advantage against selection pressures, making an individual more likely to survive and reproduce

• their offspring receive the new allele, and are said to have ‘evolved’ a new characteristic

how did Darwin and Wallace contribute to the theory of evolution?

they observed that bird have many different beak shapes

they concluded that birds with beak shapes most suited to the food they eat are more likely to survive and therefore pass this beak shape onto their offspring

give other evidence for the theory of evolution

fossils - allow us to compare extinct organisms to today’s organisms

genomic DNA - sequencing of genomes have shown how closely related we are to primates

molecular - proteins are composed of the same 20 amino acids in all organisms

what causes variation?

genetic = mutations, random fertilisation

environmental = climate, diet, culture

what is intraspecific variation?

variation within the same species

what is interspecific variation?

variation between different species

what is continuous variation?

when the individuals in a population vary within a range - no distinct categories e.g. humans can be any height within a range, not just tall or short

give some examples of continuous variation:

• milk yield in cows

• human mass

• number of leaves

• width of E. coli

• length of a flagellum

what is discontinuous variation?

when there are 2 or more distinct categories - each individual falls into only one category

give some examples of discontinuous variation:

• human blood group

• colour of courgettes

• antibiotic resistance

how can variation be caused by genes?

• differences in genotype result in variation in phenotype

• examples of variation caused by only genetic factors include blood group and antibiotic resistance in bacteria

• you inherit your genes from parents so variation caused by genetic factors is inherited

how can variation be caused by environmental factors?

• variation can be caused by differences in environment like climate, food and lifestyle

• characteristics controlled by environmental factors can change over an organism’s life

• e.g. accents, if you have pierced ears or not

how can variation be influences by genetic and environmental factors?

• genetic factors determine the characteristics and organism is born with, but environmental factors can influence how some characteristics develop

• e.g. height - genes determine how tall an organism can grow but diet or nutrient availability affect how tall they actually grow

what does the mean tell you about two samples?

how much variation there is between the two samples

what does the standard deviation tell you about a sample?

how much the values in a single sample vary about the mean

for mean what graph do we use?

normal distribution

• bell-shaped

• symmetrical about the mean

what can standard deviation sometimes be written as?

9+- 3

• mean = 9

• standard deviation = 3

• most of the values are spread between 6 and 12

what does a large sd tell you about a sample?

the values in the sample vary a lot - graph is wider

what does a small sd tell you about a sample?

most of the data is around the mean - little variation

what is the formula for calculating standard deviation?

x = value in the data set

x bar = mean

sigma = sum of

n = total no. of values

s = sd

how do adaptations develop?

because of evolution by natural selection

give some examples of behavioural adaptations?

they are ways an organisms acts that increase its chance of survival

• possums ‘play dead’ to escape attacks from predators

• scorpions dance before mating = this makes sure they attract a mate of the same species, increasing the likelihood of successful mating

give some examples of physiological adaptations?

processes inside an organisms body that increase its chance of survival