Classification & Biodiversity (Edexcel International A Level (IAL) Biology): Flashcards

The three domains are: Archaea, Bacteria, and Eukarya.

False.

Molecular phylogeny shows that Archaea and Bacteria are less closely related to each other than was previously thought, and both are distinct from Eukarya.

Phylogeny is the study of the evolutionary history of groups of organisms, including how closely related they are.

The more similar the molecules between two groups of organisms, the more recent their common ancestor.

Using DNA sequencing allows scientists to compare genotypes directly and provide clarity on evolutionary relationships, which is more accurate than using outward physical features.

Evolution is the process by which species change over time through natural selection, resulting in increased variety of life on Earth.

Human activities have threatened many species with extinction, reducing the variety of life on Earth.

The global human population has been growing exponentially for the last 150 years.

The two main reasons are improved technology leading to more food (increasing birth rate), and improved medicine and health care (decreasing death rate).

Habitat fragmentation is when a natural habitat is divided into smaller, isolated sections, increasing the risk of inbreeding and local extinction.

False.

Deforestation is one of the most damaging forms of habitat destruction because forests often have the highest levels of biodiversity.

Overexploitation occurs when resources are used up faster than they can be replaced.

Modern agriculture reduces biodiversity by creating monocultures, removing hedgerows, and increasing the use of fertilisers and pesticides, all of which harm natural habitats and non-target species.

Climate change caused by humans is leading to increased frequency of extreme weather events and changing weather patterns.

Ocean acidification, caused by increased CO₂ dissolving in seawater, lowers the pH and affects organisms like corals and plankton that need calcium carbonate for their shells, thus threatening marine biodiversity.

Biodiversity is the variety of all living organisms that exists within and between all forms of life, including genes, species, and habitats within a region.

Biodiversity can be assessed at three different levels: the number and range of ecosystems and habitats, the number and abundance of species, and the genetic variation within each species.

Biodiversity is important for ecosystem resilience because it allows ecosystems to resist changes in the environment by providing a variety of genes, species, and habitats.

Ecosystem or habitat diversity is the range of different ecosystems or habitats within a particular area or region.

True.

High habitat diversity typically leads to high biodiversity.

Species richness is the number of species within an ecosystem.

Ecosystems with high species diversity are usually more stable and resilient to environmental changes.

Genetic diversity within a species is the diversity of alleles and genes in the genome of that species.

Inbreeding in small, isolated populations leads to a high proportion of individuals being homozygous for many genes, which can lead to more common genetic diseases caused by recessive alleles.

Endemism is when certain species are found only in one particular area of the world. Endemic species are at risk of extinction due to their limited range.

A habitat is the place where an organism lives.

Species richness is the number of species within a community.

A community is a group of populations of different species living in the same place at the same time that interact with each other.

Species richness can be misleading because it does not take into account the number of individuals of each species, only the total number of species.

Species abundance is a measure of the relative number of individuals in the different species within a given area.

Conservationists often favour the use of an index of diversity as it takes into account species number and evenness.

Random sampling is used to estimate the distribution and abundance of species in a way that avoids sampling bias.

A quadrat is a square frame used to mark off an area for sampling organisms, especially plants.

Quadrats must be laid randomly in the area to avoid sampling bias.

Two sampling techniques are sweeping nets (for insects) and pitfall traps (for ground-dwelling invertebrates).

Genetic diversity refers to the different alleles that occur within the gene pool of a species or a population.

Organisms that have two different alleles at a particular gene locus are known as heterozygotes.

A higher heterozygosity index indicates greater genetic diversity within the population.

Heterozygosity index = number of heterozygotes ÷ number of individuals in the population

A higher value indicates greater genetic diversity within the species.

Species diversity is a measure of the number of different species in an area and the abundance of individuals within each species.

An index of diversity is a measurement that describes the relationship between the number of species present and the abundance of each species in a community.

A higher value of the index of diversity indicates a greater level of biodiversity in that area, meaning more species and a more even distribution of individuals among those species.

The formula for the index of diversity is D = N(N-1)/Σn(n-1), where N is the total number of organisms and n is the total number of organisms for a single species.

To calculate the index of diversity:

First, calculate N(N-1) for the whole community.

Second, calculate n(n-1) for each species and sum them.

Third, divide the first value by the sum to get the index of diversity.

To find the index of diversity, first calculate N(N-1) for the community, then calculate n(n-1) for each species and sum the results.

False.

You are not expected to memorise the formula, but you must know how to use it and understand what the calculated values mean.

Calculating the index of diversity for different habitats allows you to compare the species diversity between them objectively.

A niche is the role a species plays within its habitat, including its biotic and abiotic interactions.

A habitat is the place where a species lives, while a niche is the role the species plays within that habitat, including its interactions with other organisms and the environment.

A niche can only be occupied by one, making each species' niche unique.

If two species try to occupy the same niche, they will compete for the same resources. One species will be more successful and out-compete the other, which may be forced to find a new niche or go extinct.

The three North American warbler species avoid competition by feeding at different heights within the trees, allowing them to co-exist in the same habitat.

An adaptation is a feature of an organism that increases its chances of surviving and reproducing.

The three main types of adaptations are anatomical, behavioural and physiological.

Anatomical adaptations are structural features, behavioural adaptations are ways an organism acts, and physiological adaptations are internal processes.

False.

A species must be adapted to both biotic and abiotic factors to occupy its unique niche.

A biotic adaptation could be a rabbit's speed to escape predators, and an abiotic adaptation could be a camel's ability to conserve water.

Reproductive isolation is when changes in alleles or phenotypes prevent individuals of the same population from successfully breeding with each other, resulting in no production of fertile offspring.

Organisms that belong to the same species share the same characteristics and are able to produce fertile offspring.

Three types of changes that can lead to reproductive isolation are seasonal changes, mechanical changes, and behavioural changes.

Mechanical changes involve alterations to an organism’s genitalia that prevent successful mating.

Allopatric speciation is the formation of new species when populations of a species become reproductively isolated by geographical barriers.

True.

Sympatric speciation happens when populations become reproductively isolated by ecological or behavioural means within the same geographical area.

A population separated by a geographical barrier, like a mountain or river, is an example of allopatric speciation.

A mutation is a change in the DNA base sequence, which is the primary source of genetic variation in a population.

The primary source of genetic variation in a population is mutation.

Natural selection increases the frequency of advantageous alleles over generations because individuals with higher fitness are more likely to survive and reproduce.

Rabbits with brown fur have a selection advantage over those with white fur because they are more likely to survive and reproduce.

The Hardy-Weinberg principle states that allele frequencies in a population will not change from one generation to the next if certain conditions are met.

According to the Hardy-Weinberg equation, p + q = 1 when considering two alleles at a gene locus.

In the Hardy-Weinberg equation, p represents the frequency of the dominant allele and q represents the frequency of the recessive allele.

The population bottleneck effect occurs when a dramatic event reduces the size of a population, leading to a significant decrease in its gene pool and changes in allele frequencies.

p² + 2pq + q² = 1

where p² = frequency of the homozygous dominant genotype, 2pq = frequency of the heterozygous genotype, and q² = frequency of the homozygous recessive genotype (p = frequency of the dominant allele, q = frequency of the recessive allele).

An endangered species is a species that is being threatened with extinction.

It is important to conserve endangered species to prevent them from going extinct and to maintain biodiversity.

False.

Ideally, a species should be kept in its natural habitat where all the support systems it needs are present.

Endangered species can be placed in captivity such as zoos or botanic gardens.

A seed bank is a facility that conserves plant diversity by drying and storing seeds in a temperature-controlled environment.

Seeds of the same species are collected from different sites to maintain genetic diversity.

Seed banks allow for the preservation of plant species and can provide seeds to grow plants again if they go extinct in the wild.

Captive breeding is breeding individuals in captivity to produce offspring for release into the wild.

One disadvantage is that captive breeding of small populations can reduce genetic diversity.

Reintroducing plants and animals into the wild can help prevent them from going extinct and contribute to restoring lost or degraded habitats.

Zoos carry out scientific research to improve breeding and reintroduction success, and they educate the public to raise awareness and support for conservation.