18. Classification, Biodiversity and Conservation

For example, two bear populations may look different and use different habitats and foods, supporting separate morphological and ecological classifications. If they interbreed and produce fertile offspring, the biological concept instead supports treating them as the same species. The answer depends on the stated concept and evidence.

Use the classification in this order:

1. Ask whether the cell is prokaryotic or eukaryotic.
2. If prokaryotic, keep Bacteria and Archaea as separate possible domains rather than treating “prokaryote” as a domain.
3. Use molecular evidence alongside cell organisation before assigning the domain.
4. State the result as Bacteria, Archaea or Eukarya; detailed Archaea–Bacteria differences and lower Eukaryotic kingdoms are separate questions.

First establish that the organism is prokaryotic, then compare evidence from all three features. Lack of a nucleus narrows the classification to Archaea or Bacteria but does not decide between them.

At a higher rank, the group contains more organisms with less similarity between them. Moving down the nested hierarchy applies more shared classification evidence, so the group contains fewer organisms with greater similarity. Species is the lowest rank in this sequence.

Use the hierarchy in this order:

1. Confirm the organism belongs to Eukarya.
2. Place it in a kingdom, then progressively narrower phylum, class, order, family, genus and species groups.
3. Treat each lower group as nested within the preceding one, not as an unrelated label.
4. Use the evidence appropriate to the rank; do not substitute a kingdom name for a species identification.

Compare several features together. A cell wall does not by itself mean Plantae: fungal walls contain chitin, plant walls contain cellulose, and some protoctists also have walls. Likewise, both fungi and animals are heterotrophic, but fungi digest externally and absorb products whereas animals ingest food.

Use the classification in this order:

1. Identify whether the viral genome is DNA or RNA.
2. Determine whether that genome is single-stranded or double-stranded.
3. Report the combination as the virus classification; do not use the host organism to replace the genome evidence.
4. Keep the boundary clear: this is a nucleic-acid classification of an acellular, host-dependent entity, not a domain or kingdom assignment.

Niche overlap means two species use some of the same resources or conditions. The more their roles and resource use overlap, the greater the potential for competition; distinct resource use can allow different species to fit into the same ecosystem. This is a relationship-level interpretation, not a biodiversity count or an automatic proof of competition.

Use the terms in this order:

1. Name the ecosystem as the interacting living-and-non-living system.
2. Identify the habitat as the place occupied by a species.
3. Describe the niche through energy use, physical conditions and interactions.
4. Compare niches when explaining overlap, possible competition or how multiple species can occupy an ecosystem; keep measurement of biodiversity for a separate assessment.

Species richness is only the number of species. Species diversity also considers evenness: an area can contain many species but still have lower species diversity if most individuals belong to one or two species. Keep these terms separate when interpreting evidence.

Biodiversity can support ecosystem resilience because variation provides more ways for populations and ecosystems to respond to environmental change. This is a general ecological relationship, not a guarantee that every diverse ecosystem resists every disturbance.

A less biased sample is more likely to represent the whole area, so an estimate can be generalised with greater confidence. Repetition also reduces the influence of an unusual sampling point and allows variation between samples to be assessed.

Here $N$ is estimated population size, $n_1$ is the first sample, $n_2$ is the whole second sample and $m_2$ is marked animals recaptured. If 27 frogs are marked, 33 are caught later and 13 are marked, $N=(27\times33)/13=68.5$, reported as 69 animals.

A sample contains 6 individuals of species A, 3 of B and 1 of C, so $N=10$. $D=1-[(6/10)^2+(3/10)^2+(1/10)^2]=1-(0.36+0.09+0.01)=0.54$. A community dominated by one species would have a lower value.

Pressures can reinforce one another. Habitat loss may crowd organisms into smaller areas and increase competition. As a population shrinks, loss of genetic variation and inbreeding can reduce its ability to respond to further change, increasing the chance that the decline continues.

These reasons are interdependent rather than isolated: genetic and species diversity can support ecosystem resilience; functioning ecosystems provide services and resources; and those benefits affect human wellbeing and future choices. The evidence supports a general reason to maintain biodiversity, not a guarantee that every diverse ecosystem resists every disturbance.

Choose the method to match the threat and biological need. In situ protection maintains the whole habitat but depends on effective management and community acceptance. Ex situ storage or captivity can protect a small or isolated population, but it costs resources, may not reproduce the natural habitat, and small captive populations can lose genetic diversity. Long-term success also depends on a suitable habitat or use for the conserved material.

In a typical IVF programme: stimulate egg maturation → collect eggs and sperm → fertilise outside the body → check early embryos → transfer a selected embryo to a recipient uterus → monitor pregnancy and birth. The offspring's nuclear genes come from the egg and sperm donors, not from the surrogate.

The risk chain is: few natural predators, competitors or pathogens → rapid population increase → competition for prey, nutrients, light or space, successful predation or introduction of disease → native-population decline and reduced biodiversity/productivity. Human health, travel and economic costs can also be affected.

The tools can complement each other: an IUCN assessment may show that trade contributes to risk, while CITES controls the international trade route. A species can still receive CITES protection even when IUCN data are insufficient, because the organisations use different processes.