biodiversity

how has variety of life changed over time?

variety generally increases as new species form
human activity is threatening much of life on the planet

what are the 4 main human factors affecting biodiversity today?

habitat destruction, overexploitation, agriculture, climate change

how is habitat destruction affecting biodiversity?

land cleared for human needs through deforestation e.g. agriculture, housing, transport results in habitat loss and habitat fragmentation (habitats divided into small areas, populations more likely to suffer from inbreeding or local extinction)

how is overexploitation affecting biodiversity?

deforestation - trees are removed but not replaced by replanting + the rate at which trees are being removed exceeds the rate at which they are growing back
fish stocks - knock on effect on organisms that feed on exploited fish species
hunting - wild, non-farmed species are being hunted and removed more quickly than wild populations can be replenished e.g. bush meat

how is agriculture affecting biodiversity?

monocultures - support much lower levels of biodiversity
destruction of hedgerows - important habitat for many insects and birds, destruction removes habitat and biodiversity it supports
fertilisers - leach into waterways, causing eutrophication which can lead to death of many fish
pesticides - kills pests but also many non-target species e.g. bees

how is human caused climate change affecting biodiversity?

causing weather patterns to change and increasing frequency of extreme weather events, occurring too fast for species to adapt → extinction
global warming - species move to higher altitudes, but cannot compete with/out-compete species already present in habitats → decreased biodiversity + more CO2 dissolving in seawater causes ocean acidification and increased ocean temp causes more coral-bleaching events

what is biodiversity?

the variety of living organisms that exist within and between all forms of life

what are the three levels at which biodiversity is assessed?

number and range of different ecosystems and habitats, the number of species and their relative abundance, the genetic variation within each species

what is ecosystem or habitat diversity?

the range of different ecosystems or habitats within a particular area or region
large number of different habitats = high biodiversity e.g. coral reef
low number of different habitats = low biodiversity e.g sandy deserts

what is species diversity?

the number of different species in an ecosystem (species richness) and the abundance of each present
greater number of species = greater abundance of individuals from each species = greater species diversity

what is an advantage of an ecosystem with high species diversity?

usually more stable than those with lower species diversity as they are more resilient to environmental changes

what is genetic diversity?

the diversity of alleles and genes in the genome of species
can be observed between populations of the same species and within a single population

why is genetic diversity important in a species?

it helps a population adapt to and survive biotic or abiotic changes in the environment

what is genetic diversity like in small or isolated population?

it is limited
inbreeding leads to a high proportion of homozygous individuals for many genes, resulting in lower genetic diversity
genetic diseases caused by recessive alleles can become more common

what is endemism?

when a species is found only in one geographical location and they do not naturally occur anywhere else
at risk of extinction due to limited range

what is a habitat?

a place where an organism lives

how can biodiversity be measured within a habitat?

species richness, the number of species within a community

why can species richness be a misleading indicator of diversity?

does not take into account the number of individuals of each species
instead, species abundance can be used - a measure of the relative number of individuals in the different species within a given area

how can the biodiversity of different habitats be compared?

the index of biodiversity
d = N(N - 1) / {n(n - 1)
N = total number of organisms of all species, n = total number of organisms of each species

how can the genetic diversity within a species be determined?

the heterozygosity index
H = number of heterozygotes / number of individuals in the population

what is a niche?

the role that a species plays within its habitat, including the biotic interactions of the species and the abiotic interactions
only one species can occupy a niche, every species has its own unique nuche

what happens when two species try to occupy the same niche?

they will compete with each other for the same resources
one of the species will be more successful and outcompete the other until only one is left and the other is forced to occupy a new niche / go extinct from habitat

what are adaptations?

features of organisms that increase their chances of surviving and reproducing

what are the three types of adaptations?

anatomical - structural features e,g, claws
behavioural
physiological - processes inside the body e.g. venom production

what is the process for natural selection leading to adaptation and evolution?

variation due to random mutations introduces new alleles into a population
some alleles provide an advantage, making an individual more likely to survive and reproduce
they pass on their alleles to their offspring so that the advantageous alleles increase in frequency over generations, resulting in evolution

what can affect the chance of survival of an organism?

selection pressures which include predation, disease, and competition
they make it difficult for all individuals in a population to survive

how do selection pressures encourage evolution through natural selection?

increase the chances of individuals with a favourable phenotype surviving and reproducing over others

what is the hardy-weinberg principle?

the allele frequencies of a gene within a population will not change from one generation to the next

what conditions must be met for the hardy-weinberg principle?

mating must be random, the population is infinitely large. there is no migration, mutation or natural selection

what does the hardy-weinberg equation calculate?

allele and genotype frequencies within populations

what is the hardy-weinberg equation?

frequency of homozygous dominant individuals + frequency of heterozygous individuals + frequency of homozygous recessive individuals = 1
p2 + 2pq + q2 = 1

how should i start off the hardy-weinberg equation?

by calculating the proportion of individuals that display the recessive phenotype

when does reproductive isolation occur?

changes in the alleles and phenotypes of some individuals in a population prevent them from successfully breeding with unchanged individuals in the population

what are three examples of allele and phenotype changes that can lead to reproductive isolation?

seasonal changes - different mating or flowering seasons
mechanical changes - changes in genitalia
behavioural changes - changes in courtship behaviours

what is speciation?

populations of a species become separated from each other by natural or man-made geographical barriers

what is the process of speciation?

geographical barriers isolate populations of a species
selection pressures and random mutations can change the allele frequencies within both populations, leading to natural selection
over time, these populations will form separate species

what is classification?

a means of sorting organisms into taxa based on their relationships, using both genotypes and phenotypes

what are the ranks in the taxonomic classification?

domain, kingdom, phylum, class, order, family, genus, species

what is the species concept?

when many different species can be grouped together in the same genus, but still are separate species as they cannot produce fertile offspring

what were early classification systems like and what improved them?

early systems only relied on the phenotype of organisms to classify them
there are many non-related organisms with similar phenotypes
advances in technology e.g. DNA sequencing has made it possible to compare genotypes

what are the five kingdoms?

prokaryotae, protoctista, fungi, plantae, animalia,

what is kingdom prokaryotae?

prokaryotic cells like bacteria e.g. cyanobacteria

what is kingdom protoctista?

eukaryotes that photosynthesis or feed on organic matter not included in other kingdoms e.g. algae

what is kingdom fungi?

multicellular eukaryotes that are heterotrophs that absorb nutrients from decaying matter

what is kingdom plantae?

multicellular eukaryotes that are autotrophs; organisms that make their own organic molecules by photosynthesis

what is kingdom animalia?

multicellular eukaryotes that are heterotrophs; organisms that obtain energy as organic molecules by ingesting material from other organisms

what are binomials?

the scientific names given to individual species
consists of organism’s genus and species

why are binomials useful?

allow for universal identification of species, binomial for a species is same globally

what does the three domain system consist of?

archaea, bacteria, eukarya

what information is the the three domain system based on?

molecular phenology

what is molecular phenology?

the similarities / differences of molecules between groups of organisms to determine how closely related they are
the more similar molecules = more recent common ancestor they share

how did molecular phenology lead to the formation of the three domain system?

kingdom prokaryotae would be reclassified into two separate domains - archaea + bacteria
archaea + bacteria less closely related than previously thought