Topic 18: Classification, biodiversity and conservation

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18.1 Classification

 

​Students should be able to:

1) discuss the meaning of the term species, limited to the biological species concept, morphological species concept and ecological species concept

2) describe the classification of organisms into three domains: Archaea, Bacteria and Eukarya

3) state that Archaea and Bacteria are prokaryotes and that there are differences between them, limited to differences in membrane lipids, ribosomal RNA and composition of cell walls

4) describe the classification of organisms in the Eukarya domain into the taxonomic hierarchy of kingdom, phylum, class, order, family, genus and species

5) outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae and Animalia

6) outline how viruses are classified, limited to the type of nucleic acid (RNA or DNA) and whether this is single stranded or double stranded

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1. Discuss the meaning of the term species, limited to the biological species concept, morphological species concept, and ecological species concept

The term species is fundamental in biology and refers to a group of organisms that share common characteristics and can be classified together. However, there are several ways to define what a species is, each with a slightly different focus:

• The biological species concept defines a species as a group of individuals that can interbreed successfully in nature to produce fertile offspring. This means that members of the same species share gene pools and can exchange genetic material, but they are reproductively isolated from members of other species. For example, horses and donkeys are different species because their offspring (mules) are sterile and cannot reproduce.
   

• The morphological species concept classifies species based on observable physical characteristics such as shape, size, and structural features. This method is often used when reproductive information is unavailable, such as with fossils or asexually reproducing organisms. Organisms that look very similar in form and structure are grouped into the same species under this concept.
   

• The ecological species concept defines species based on their ecological niche, which includes how they interact with their environment and other organisms. According to this concept, species are groups that occupy distinct roles in ecosystems. For example, two populations of similar-looking insects that feed on different plants and never encounter each other might be considered separate species because of their ecological differences.
   

Each concept has its advantages and limitations, and biologists often use a combination to accurately define species in nature.

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2. Describe the classification of organisms into three domains: Archaea, Bacteria, and Eukarya

Modern biological classification recognizes three broad domains that group all life forms based on genetic and cellular characteristics:

• Archaea are single-celled organisms similar to bacteria in appearance but genetically and biochemically distinct. They often live in extreme environments, such as hot springs or salty lakes, and have unique membrane lipids and enzymes adapted to harsh conditions.
   

• Bacteria are also single-celled prokaryotes but differ from Archaea in their cell wall composition and genetic sequences. They are found almost everywhere, including soil, water, and inside other organisms. Many bacteria play essential roles in processes like nitrogen fixation, digestion, and decomposition.
   

• Eukarya include all organisms whose cells have a nucleus enclosed within membranes. This domain encompasses a wide variety of life, including plants, animals, fungi, and protists. Eukaryotic cells are generally larger and more complex than prokaryotic cells.
   

The three-domain system is based on differences in ribosomal RNA sequences and cellular structures and is a more accurate reflection of evolutionary relationships than the older two-kingdom or five-kingdom systems.

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3. State that Archaea and Bacteria are prokaryotes and that there are differences between them, limited to differences in membrane lipids, ribosomal RNA, and composition of cell walls

Both Archaea and Bacteria are classified as prokaryotes, meaning their cells lack a true nucleus and membrane-bound organelles. Despite their similar appearance under the microscope, they differ significantly in some key biochemical and genetic traits:

• The membrane lipids in Archaea contain ether bonds between glycerol and their hydrophobic side chains, whereas bacteria have ester bonds in their membrane lipids. This difference makes archaeal membranes more stable in extreme environments.
   

• The ribosomal RNA (rRNA) sequences in Archaea are distinct from those in Bacteria, reflecting a fundamental evolutionary divergence. These differences are used to classify them into separate domains.
   

• The composition of their cell walls also differs. Many bacteria have cell walls made of peptidoglycan, a polymer that provides structural strength. In contrast, Archaea do not have peptidoglycan; instead, their cell walls may contain other polymers like pseudopeptidoglycan or proteins, making them chemically distinct.
   

These differences are important for understanding their biology, ecology, and evolutionary history.

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4. Describe the classification of organisms in the Eukarya domain into the taxonomic hierarchy of kingdom, phylum, class, order, family, genus, and species

Within the domain Eukarya, organisms are further classified using a hierarchical system called taxonomic hierarchy, which organizes living things from broad to specific groups:

• The broadest level after domain is the kingdom. For example, Animalia, Plantae, Fungi, and Protista are kingdoms within Eukarya.
   

• Below kingdom is the phylum, which groups organisms based on major structural features or body plans. For example, Chordata is a phylum containing animals with a backbone.
   

• Next is class, a division within a phylum. Mammalia is a class within Chordata and includes all mammals.
   

• Order groups organisms within a class that share more specific characteristics. For example, Carnivora is an order of meat-eating mammals.
   

• Family groups closely related genera (plural of genus). For example, Felidae is the cat family.
   

• Genus is a group of species that are closely related and share a common ancestor. For example, Panthera includes lions and tigers.
   

• Finally, species is the most specific classification level, representing individuals that can breed and produce fertile offspring.
   

This hierarchical system allows scientists to organize the vast diversity of eukaryotic life into manageable categories and study evolutionary relationships.

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5. Outline the characteristic features of the kingdoms Protoctista, Fungi, Plantae, and Animalia

Each kingdom in the Eukarya domain has unique features that distinguish its members:

• Protoctista (or Protista) are mostly unicellular or simple multicellular organisms that do not fit into other kingdoms. They have eukaryotic cells and may have animal-like (protozoa), plant-like (algae), or fungus-like characteristics. For example, amoebae move using pseudopodia, while algae photosynthesize.
   

• Fungi are mostly multicellular organisms that have cell walls made of chitin. They obtain nutrients by absorbing organic material from dead or living organisms (saprotrophic nutrition). Examples include mushrooms and yeasts. Fungi reproduce using spores.
   

• Plantae are multicellular, photosynthetic organisms with cellulose cell walls. They produce their own food through photosynthesis using chlorophyll. Plants have complex structures such as roots, stems, and leaves. They reproduce sexually by seeds or spores.
   

• Animalia includes multicellular organisms that do not have cell walls. Animals obtain energy by consuming other organisms (heterotrophic nutrition). They usually have specialized tissues and organs and exhibit movement at some stage in their life cycle.
   

Understanding these kingdoms helps categorize the immense variety of eukaryotic life.

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6. Outline how viruses are classified, limited to the type of nucleic acid (RNA or DNA) and whether this is single stranded or double stranded

Viruses are not classified within the domain system because they are not considered living organisms by many biologists. Instead, viruses are classified based on the type of nucleic acid they contain and its structure:

• Viruses can have DNA or RNA as their genetic material.
   

• This genetic material can be either single-stranded or double-stranded.
   

For example, the influenza virus contains single-stranded RNA, whereas the herpes virus contains double-stranded DNA. This classification is important because it influences how the virus replicates and how it interacts with host cells

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18.2 Biodiversity

 

​Students should be able to:

1) define the terms ecosystem and niche

​2) explain that biodiversity can be assessed at different levels, including:

• the number and range of different ecosystems and habitats

• the number of species and their relative abundance

• the genetic variation within each species

3) explain the importance of random sampling in determining the biodiversity of an area

​4) describe and use suitable methods to assess the distribution and abundance of organisms in an area, limited to frame quadrats, line transects, belt transects and mark-release recapture using the Lincoln index

5) use Spearman’s rank correlation and Pearson’s linear correlation to analyse the relationships between two variables, including how biotic and abiotic factors affect the distribution and abundance of species

6) use Simpson’s index of diversity (D) to calculate the biodiversity of an area, and state the significance of different values of D

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1. Define the terms ecosystem and niche

• An ecosystem is a community of living organisms interacting with each other and with their physical environment in a specific area. It includes all the biotic factors (plants, animals, microorganisms) and abiotic factors (soil, water, climate) that together form a functional unit. For example, a forest ecosystem consists of trees, animals, insects, fungi, soil, water, and air.
   

• A niche is the specific role or function an organism has within its ecosystem, including how it obtains food, its habitat, and its interactions with other species. It is essentially the organism’s "job" or way of life in the ecosystem. No two species can occupy exactly the same niche for a long time because of competition

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2. Explain that biodiversity can be assessed at different levels, including the number and range of different ecosystems and habitats, the number of species and their relative abundance, and the genetic variation within each species

Biodiversity refers to the variety and variability of life on Earth, and it can be evaluated at several levels:

• The number and variety of ecosystems and habitats in a region show ecosystem diversity. Different habitats like forests, lakes, and grasslands support different communities of organisms.
   

• Species diversity includes both the number of different species in an area (species richness) and their relative population sizes (species abundance). An area with many species that are evenly represented is more diverse.
   

• Genetic diversity is the variety of genes within a species. This genetic variation enables populations to adapt to changing environments and resist diseases.
   

Assessing biodiversity at all these levels is essential for conservation and understanding ecological health.

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3. Explain the importance of random sampling in determining the biodiversity of an area

Random sampling is a method used to obtain an unbiased representation of organisms in a habitat because it ensures that every individual or location has an equal chance of being studied. This is important because:

• It avoids selection bias, which might occur if only easy-to-access or particularly interesting areas are sampled.
   

• It provides more reliable and reproducible data about the true diversity and abundance of species in an area.
   

• Random sampling allows ecologists to make general conclusions about biodiversity without studying every single organism.
   

 

4. Describe and use suitable methods to assess the distribution and abundance of organisms in an area, limited to frame quadrats, line transects, belt transects, and mark-release-recapture using the Lincoln index

• Frame quadrats are square frames of known size placed randomly in a habitat to count organisms within that area. This method estimates population density and distribution.
   

• Line transects involve stretching a line (such as a tape) across a habitat and recording organisms touching the line at intervals. This method helps assess how organisms are distributed along an environmental gradient.
   

• Belt transects combine line transects and quadrats by placing quadrats along the line at regular intervals to measure abundance and distribution across a habitat.
   

• Mark-release-recapture is used for mobile animals. A sample of animals is caught, marked harmlessly, and released. After some time, a second sample is caught, and the number of marked animals recaptured is counted. The Lincoln index formula estimates population size.

This method assumes that marked individuals mix fully back into the population and that marks are not lost.

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18.3 Conservation

 

​Students should be able to:

1) explain why populations and species can become extinct as a result of:

• climate change

• competition

• hunting by humans

• degradation and loss of habitats

2) outline reasons for the need to maintain biodiversity

3) outline the roles of zoos, botanic gardens, conserved areas (including national parks and marine parks), ‘frozen zoos’ and seed banks, in the conservation of endangered species

4) describe methods of assisted reproduction used in the conservation of endangered mammals, limited to IVF, embryo transfer and surrogacy

5) explain reasons for controlling invasive alien species

6) outline the role in conservation of the International Union for Conservation of Nature (IUCN) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

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1. Explain why populations and species can become extinct as a result of climate change, competition, hunting by humans, and degradation and loss of habitats

Populations and species can become extinct when their survival becomes impossible due to several factors:

• Climate change alters temperature, precipitation, and weather patterns, which can destroy habitats and food sources, forcing species to migrate or adapt quickly. Those unable to cope with these changes may die out.
   

• Competition occurs when species compete for the same limited resources such as food, space, or mates. If one species is better adapted, it may outcompete others, leading to their decline or extinction.
   

• Hunting by humans can drastically reduce populations, especially when species are targeted for food, trophies, or traditional medicine faster than they can reproduce.
   

• Degradation and loss of habitats through deforestation, urbanization, and pollution remove the physical space and resources organisms need, causing population declines and eventual extinction.
   

Understanding these causes is essential for developing effective conservation strategies.

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2. Outline reasons for the need to maintain biodiversity

Maintaining biodiversity is crucial for several reasons:

• It ensures ecosystem stability and resilience, allowing ecosystems to recover from disturbances.
   

• Biodiversity provides a wide range of resources for humans, including food, medicine, and raw materials.
   

• Genetic diversity within species allows adaptation to changing environments and diseases.
   

• Biodiversity has aesthetic, cultural, and scientific value, enriching human life and knowledge.
   

• The loss of biodiversity can disrupt ecosystem services, such as pollination and water purification, vital for human survival.

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3. Outline the roles of zoos, botanic gardens, conserved areas (including national parks and marine parks), ‘frozen zoos’ and seed banks in the conservation of endangered species

• Zoos provide captive breeding programs, education, and research opportunities to help preserve endangered animals.
   

• Botanic gardens conserve plant species, especially rare or endangered ones, and serve as centers for research and public awareness.
   

• Conserved areas like national parks and marine parks protect habitats from human interference, allowing ecosystems to function naturally and species to thrive.
   

• Frozen zoos store genetic material such as sperm, eggs, or embryos at very low temperatures for future use in breeding or research.
   

• Seed banks collect and store seeds from a variety of plants to safeguard genetic diversity and enable future restoration or reintroduction.
   

Together, these institutions play complementary roles in safeguarding biodiversity.

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4. Describe methods of assisted reproduction used in the conservation of endangered mammals, limited to IVF, embryo transfer, and surrogacy

• In vitro fertilization (IVF) involves fertilizing eggs with sperm outside the body in a laboratory setting, then implanting the resulting embryos into a female’s uterus.
   

• Embryo transfer involves moving embryos from a genetically valuable female into the uterus of a surrogate mother who carries the pregnancy to term.
   

• Surrogacy refers to using a different female to carry and give birth to offspring on behalf of the biological parents, often used when the biological mother cannot gestate.
   

These techniques help increase population numbers and genetic diversity in endangered mammals.

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5. Explain reasons for controlling invasive alien species

Invasive alien species are organisms introduced by humans to new environments where they do not naturally occur. They can cause harm by:

• Competing with native species for resources, often leading to declines or extinction of native species.
   

• Preying on native species that have no evolved defenses.
   

• Introducing new diseases or parasites.
   

• Altering habitats and disrupting ecosystem processes.
   

Controlling invasive species is necessary to protect native biodiversity and ecosystem health.

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6. Outline the role in conservation of the International Union for Conservation of Nature (IUCN) and the Convention on International Trade in Endangered Species of Wild Fauna and Flora (CITES)

• The IUCN maintains the Red List, which assesses the conservation status of species worldwide, identifying those at risk of extinction and guiding conservation priorities.
   

• CITES is an international agreement regulating trade in endangered species of wild animals and plants to ensure that such trade does not threaten their survival. It lists species in appendices according to the level of protection needed.
   

Both organizations provide frameworks for international cooperation in biodiversity conservation.