Topic 4: Biodiversity and Natural Resources Flashcards
4.2 i) Outline what biodiversity is and what it includes?
Biodiversity is the variety of living organisms in an environment. It includes:
- Species diversity:
Species richness - the number of different species in a given habitat.
Species evenness - how close in numbers each species is in an environment.
- Genetic diversity: the variation of alleles within a species (or within a population of a species).
4.2 i) Explain the term ‘endemism’
Endemism is when a species is unique to a single place (it isn’t found anywhere else in the world).
4.2 ii) How can biodiversity be measured within a habitat using species richness?
Species richness is the number of different species in an area. Counting the number of different species is too time-consuming. Instead, a sample of the population is taken and estimates about the whole habitat are based on the sample:
Choose a small area to sample within the habitat being studied. To avoid bias, the sample should be chosen randomly (i.e. using a random number generator to select coordinates). Count the number of individuals of each species in the sample area (e.g. using a quadrat). Repeat the process to gain a better indication of the whole habitat.
4.2 ii) How can biodiversity be measured within a species using genetic diversity?
You can measure the genetic diversity within a species using the heterozygosity index (heterozygotes have two different alleles at a particular locus).
H = no. of heterozygotes / no. of individuals in the population
A higher proportion of heterozygotes means that the population has a high genetic diversity.
4.2 iii) How can biodiversity be compared in different habitats?
Biodiversity can be compared in different habitats using a formula to calculate an index of diversity (D) - this formula takes account of both species richness and evenness:
D = N(N - 1) / Σn(n - 1)
Where:
N = The total no. of organisms (of all species)
n = The total no. of organism in one species
Σ = The sum of
The higher the number, the more diverse the area is.
A highly diverse habitat would have high species richness and high species evenness. In comparison, a community with an identical number of species, but which is dominates by one of them, is considered to be less diverse. Species evenness often has a greater impact than species richness in terms of biodiversity.
4.3 Outline and explain the concept of a ‘niche’.
A niche can be defined as the way an organism exploits its environment. The niche a species occupies within an habitat includes its interactions with other living organisms, and its interactions with non-living organisms. Every species occupies its own unique niche. If two species live in the same habitat and occupy the same niche, they will compete directly with each other - the better adapted organism will out-compete the other and exclude it from the habitat.
4.3 Outline and discuss three examples of adaption of organisms to their environment.
Behavioural adaptations are any actions by organisms that help them to survive or reproduce.
Physiological adaptations are internal processes (often systematic responses to an external stimuli) that help organism survive or reproduce.
Anatomical adaptations are structural features of an organisms body that help it survive and reproduce.
4.4 Explain how natural selection can lead to adaptation and evolution.
A selection pressure can affect an organisms chance of survival and reproduction. Genetic variations within a species, a result of random mutations, crossing over and independent assortment (during meiosis), can result in individuals who have advantageous genes, and therefore an advantageous phenotype. These individuals have a selective advantage, and are more likely to survive, reproduce and pass on their advantageous alleles to their offspring. Over time, the number of individuals with the advantageous alleles increases. Evolution is therefore a change in allele frequency over time.
4.4 List three factors which affect the ability of a population to adapt to new conditions.
- The strength of the selection pressure.
- The size of the gene pool.
- The reproductive rate of the organism.
4.5 i) Outline how the Hardy-Weinberg equation can be used to predict allele frequency.
When a gene has two alleles, you can calculate the frequency of one of the alleles given the frequency of the other allele:
p + q = 1
p = the frequency of the dominant allele
q = the frequency of the recessive allele
You can calculate the frequency of one genotype, given the frequencies of the others:
p2 + 2pq + q2 = 1
p2 = the frequency of the homozygous dominant genotype
2pq = the frequency of the heterozygous genotype
q2 = = the frequency of the homozygous recessive genotype
e.g. Given the proportion of people with a heterozygous recessive genotype (qq) in a population, first convert this to a decimal, and then square root it to gain the frequency of the recessive allele (q) within a population. Then calculate the frequency of the dominant allele (p) using 1 - q = p. Using the values for p and q, you can then calculate the 2pq and p2.
4.5 i) Explain how and why the Hardy-Weinberg equation and principles can be used to see whether a change in allele frequency is occurring in a species over time.
The allele frequency (how often an allele occurs) in a population can be calculated using the Hardy-Weinberg equation.
The Hardy-Weinberg principle predicts that the frequency of alleles in a population won’t change from one generation to the next - this is on the basis that no immigration, emigration, mutations or natural selection occurs. There also needs to be random mating - where all possible genotypes can breed with each other.
If the frequency of an allele has changed between generations, the Hardy-Weinberg principle doesn’t apply - one of the above factors must have been affecting allele frequency.
4.5 ii) Outline how geographical isolation can lead to speciation.
Speciation is the development of a new species. A population can become reproductively isolated due to geographical isolation. Geographical isolation takes place when a physical barrier divides a population of a species. Environmental conditions on either side of the barrier will be slightly different, providing different selection pressures. Genetic variations within each gene pool, a result of random mutations, crossing over and independent assortment (during meiosis), can result in individuals who have advantageous genes, and therefore an advantageous phenotype. These individuals have a selective advantage, and are more likely to survive, reproduce and pass on their advantageous alleles to their offspring. Over time, the number of individuals with the advantageous alleles will increase in each population. Due to the accumulation of different genetic information in each population, they might eventually evolve into two separate species. A species is defined as a group of similar organisms that can reproduce to give fertile offspring
4.6 i) Explain what classification entails.
Classification is a means of organising the variety of life based on relationships between organisms using differences and similarities in phenotypes and genotypes. It is based around the species concept, where a species is defined as a group of similar organisms that can reproduce to give fertile offspring.
There are eight taxonomic groups:
Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species.
As you move down the hierarchy, there are more groups at each level but fewer organisms in each group. Since members of a taxon share common features (in phenotype and genotype), it is likely that they also share a common evolutionary ancestor.
4.6 i) Outline the common features of each of the five kingdoms.
1) Animalia: euakaryotic, multicellular, no cell wall, heterotrophic
2) Plantae: eukaryotic, multicellular, cell wall made from cellulose, contains chlorophyll and can photosynthesise, autotrophic
3) Fungi: eukaryotic, multicellular, chitin cell wall, heterotrophic - more specifically saprotrophic (absorbs nutrients from dead or decaying matter)
4) Prokaryotae: prokaryotic, unicelluar, no nucleus
5) Protoctista: eukaryotic, single-celled / simple multicellular organisms, usually live in water, heterotrophic / autotrophic
4.6 ii) Explain the process that leads to new taxonomic groups.
Scientists can share new discoveries through meetings and scientific journals (this allows to comment on and assess the investigation). New data is critically evaluated by the scientific community (to check that experiments are valid and conclusions fair) e.g. the research is peer-reviewed (to detect invalid claims and support valid ones) before being accepted.
4.6 ii) Outline the concept of the three domains of life.
Phylogeny is the study of evolutionary history of groups of organisms. Molecular phylogeny involves the examination of molecules (such as DNA and proteins) to see which species are related and how closely related these organisms are.
In the older, five kingdom system of classification, all organisms were placed into one of five kingdoms. In the new, three domain system, all organisms are placed into one of three domains. Organism that were in the kingdom Prokaryotae (unicellular organisms without a nucleus) are separated into two domains - the Archaea and Bacteria. The Prokaryotae were classified into two domains because molecular phylogeny suggested that Archaea and Bacteria are more distantly related than originally thought. Organisms from the other four kingdoms (organisms with cells that contain a nucleus) are placed in the third kingdom - Eukaryota.
4.7 Describe the structure an function of the cell wall.
The cell wall is a rigid structure that surrounds cell walls, made mainly of the carbohydrate cellulose. It supports plant cells.
4.7 Describe the structure an function of the middle lamella.
The middle lamella is the outermost layer of the cell. It acts as an adhesive, sticking adjacent plant cells together, and providing stability.
4.7 Describe the structure an function of plasmodesmata.
Plasmodesmata (singular: plasmodesma) are channels in the cell walls that link adjacent cells together. They allow transport of substances and communication between cells.
4.7 Describe the structure an function of pits.
Pits are regions of the cell wall where the wall is very thing. They’re arranged in pairs so that the pit in one cell is lined up with the pit in the adjacent cell. They allow transport of substances between cells.
4.7 Describe the structure an function of an amyloplast.
An amyloplast is a small organelle enclosed by a membrane, containing starch granules. They provide storage for starch grains, and convert starch back to glucose for release when the plan requires it.
4.7 Describe the structure an function of a vacuole.
The vacuole contains the cell sap, which is made up of water, enzymes, minerals and waste products. Vacuoles keep the cells turgid (preventing them from wilting) and are also involved in the breakdown and isolation of unwanted chemicals in the cell. It is surrounded by a membrane called the tonoplast, which controls what enters and leaves the vacuole.
4.9 Explain the structure and function of starch.
Starch acts as an energy storage molecule for plants. It is a mixture of two polysaccharides:
1. Amylose is a long, unbranched chain make from alpha-glucose monomers, joined with 1-4 glycosidic bonds. The position and angles of these bonds cause a coiled structure, making it compact and therefore good as a storage molecule.
2. Amylopectin is a long, branched chain made from alpha-glucose molecules, joined with both 1-4 and 1-6 glycosidic bonds. These side branches enable to enzymes to access and break down the glycosidic bonds easily, releasing glucose quickly when needed.
Starch is also insoluble in water, preventing it from effecting the concentration of water in the cell and the osmotic balance.
4.9 Explain the structure and function of cellulose.
Cellulose is formed from long, unbranched chains of β-glucose, joined by 1,4-glycosidic bonds. The glycosidic bonds are straight, so the polysaccharide remain as straight chains.
Hydrogen bonds form between the β-glucose molecules in neighbouring cellulose chains, forming cellulose microfibrils.
In the cell wall, layers of cellulose microfibrils are laid down at different angles (in a net-like arrangement). This ensures that the cell wall remains strong and supportive.
