Revision NotesA2

biological species — A group of organisms with similar morphology and physiology, which can breed together to produce fertile offspring and are reproductively isolated from other species.

This concept defines species based on their ability to interbreed and produce fertile offspring, emphasizing reproductive isolation as a key criterion. For example, two different breeds of dog can mate and have fertile puppies, making them the same biological species. However, a dog and a cat cannot produce fertile offspring, so they are different biological species.

morphological species — A group of organisms that share many physical features that distinguish them from other species.

This concept is often used when the biological species concept cannot be applied, such as for fossil species or organisms that reproduce asexually. It relies on observable physical characteristics like outward appearance (morphology) and anatomy. For instance, different types of roses in a garden all look like roses, sharing similar flower and leaf structures, allowing classification based on morphology.

ecological species — A population of individuals of the same species living in the same area at the same time.

This concept focuses on a population of organisms that share common features and occupy the same habitat at the same time, highlighting their ecological role and interactions within a specific environment. For example, a group of deer living in a particular forest at the same time, all sharing the same food sources and interacting with each other, would be considered an ecological species within that forest.

population — All of the organisms of the same species present in the same place and at the same time that can interbreed with one another.

A population is a fundamental unit in ecology and evolution, representing a group of individuals of a single species that share a common gene pool and interact within a defined geographical area and time frame. All the students in a specific biology class at a particular school during one academic year form a population of students, as they are all of the same 'species' (students), in the same place, at the same time, and can interact.

biological classification — The organisation of living and extinct organisms into systematic groups based on similarities and differences between species.

This process helps biologists manage the vast diversity of life, making it easier to study, understand, and remember the key features of different organisms by grouping them into categories. It's like organizing books in a library: you group similar books (e.g., fiction, non-fiction) into categories, then subcategories, making it easier to find and understand the collection.

taxonomy — The study and practice of naming and classifying species and groups of species within the hierarchical classification scheme.

Taxonomy is the scientific discipline concerned with the identification, naming, and classification of organisms, involving the assignment of organisms to specific taxonomic units (taxa) within a hierarchical system. A librarian who creates the system for categorizing and naming all the books in a library is doing taxonomy for books.

hierarchical classification — The arrangement of organisms into groups of different rank, from species (lowest) to domain (highest), where similar groups are nested within larger, more inclusive groups.

This system organizes life into a series of nested categories, allowing for a systematic way to show evolutionary relationships and shared characteristics, moving from very specific groups to very broad ones. It's like a set of Russian nesting dolls: each smaller doll (species) fits inside a slightly larger one (genus), and so on, up to the largest doll (domain).

taxonomic rank — One of the groups used in the hierarchical classification system for organisms, such as species, genus, family, order, class, phylum, kingdom and domain.

Each taxonomic rank represents a level in the hierarchy, with organisms at lower ranks sharing more specific characteristics and being more closely related than those at higher ranks. In a company, 'CEO', 'Manager', and 'Employee' are different ranks; similarly, 'Kingdom', 'Phylum', and 'Species' are different ranks in biological classification.

taxon (plural: taxa) — A taxonomic group of any rank, such as a particular species (e.g. Giraffa camelopardalis), a family (e.g. Elephantidae), a class (e.g. Mammalia) or a kingdom (e.g. Plantae).

A taxon is a named group of organisms at any level of the classification hierarchy, representing a concrete group of organisms that share common characteristics and are distinct from other groups. If 'class' is a taxonomic rank, then 'Mammalia' is a specific taxon within that rank, referring to all mammals.

domain — The highest taxonomic rank.

The domain is the broadest category in the hierarchical classification system, dividing all life into three major groups: Bacteria, Archaea, and Eukarya, based on fundamental differences in cell structure and molecular biology. Think of the 'domain' as the largest continent on Earth, encompassing many different countries (kingdoms) and cities (species).

kingdom — The taxonomic rank below domain.

Kingdoms are broad groupings within domains, further categorizing organisms based on general characteristics such as cell type, mode of nutrition, and body organization. The Eukarya domain is divided into four kingdoms: Protoctista, Fungi, Plantae, and Animalia. If 'domain' is a continent, then 'kingdom' is a large country within that continent, containing many different regions (phyla) and cities (species).

Bacteria — The domain that contains all prokaryotic organisms except those classified as Archaea.

Bacteria are single-celled prokaryotes characterized by the absence of a nucleus and membrane-bound organelles, having circular DNA without histone proteins, and cell walls containing peptidoglycans. Think of bacteria as the 'classic' single-celled organisms, like the common germs you might hear about, distinct from the more 'extreme' archaeans.

Archaea — The domain of prokaryotic organisms that resemble bacteria but share some features with eukaryotes.

Archaeans are prokaryotes that often inhabit extreme environments and possess unique membrane lipids, ribosomal RNA sequences more similar to eukaryotes, and cell walls without peptidoglycans, distinguishing them from Bacteria. Imagine Archaea as the 'ancient survivors' of the microbial world, thriving in conditions that most other life forms cannot tolerate.

Eukarya — The domain that contains all eukaryotic organisms: protoctists, fungi, plants and animals.

Eukarya is characterized by cells possessing a nucleus and membrane-bound organelles, with DNA arranged in linear chromosomes associated with histone proteins, and larger (80S) ribosomes in the cytosol. Think of Eukarya as all the 'complex' life forms you can see with the naked eye, plus many microscopic ones, all sharing the fundamental feature of having cells with internal compartments.

Protoctista — Kingdom of eukaryotic organisms which are single-celled or made up of groups of similar cells.

This is a highly diverse kingdom of eukaryotes that do not fit into the Fungi, Plantae, or Animalia kingdoms. They can be animal-like (protozoa) or plant-like (algae), with varying cell structures and modes of nutrition. Think of the Protoctista as the 'miscellaneous' drawer of eukaryotes; if it has a nucleus but isn't clearly a fungus, plant, or animal, it probably belongs here.

protoctist — A member of the Protoctista kingdom.

Protoctists are a diverse group of eukaryotic organisms, including single-celled forms like amoebas and paramecia, and simple multicellular forms like seaweeds, characterized by their varied cellular organization and nutritional strategies. A protoctist is like a 'biological odd job' organism; it's eukaryotic but doesn't quite fit into the more defined categories of plants, animals, or fungi.

Fungi — Kingdom of eukaryotic organisms which do not photosynthesise and have cell walls but without cellulose.

Fungi are heterotrophic eukaryotes that obtain nutrients by absorbing organic compounds from their environment, often through decomposition or parasitism. Their cell walls are typically made of chitin, not cellulose, and they reproduce via spores. Think of fungi as the 'recyclers' of the biological world; they break down dead matter and absorb nutrients, much like a compost heap.

Plantae — Kingdom of eukaryotic organisms which are multicellular, have cell walls that contain cellulose and can photosynthesise.

Plants are multicellular, autotrophic eukaryotes that produce their own food through photosynthesis, possess specialized cells forming tissues and organs, and have rigid cell walls primarily composed of cellulose. Think of plants as the 'primary producers' of most ecosystems, converting sunlight into energy, much like a solar panel converts light into electricity.

Animalia — Kingdom of eukaryotic organisms which are multicellular and heterotrophic and have a nervous system.

Animals are multicellular, heterotrophic eukaryotes that obtain food by ingestion, lack cell walls and chloroplasts, and are characterized by specialized cells, tissues, and organs, including a unique nervous system for communication. Think of animals as the 'consumers' of the biological world, actively seeking and ingesting food, and often moving and reacting to their environment.

biodiversity — The variety of ecosystems and species in an area and the genetic diversity within each species.

Biodiversity encompasses three levels: the diversity of ecosystems and habitats, the number and relative abundance of different species, and the genetic variation within individual species. High biodiversity generally leads to more stable and resilient ecosystems. Imagine a diverse library with many different genres of books (ecosystems), many different authors (species), and many different editions or translations of each book (genetic diversity).

endemic — Of species, a species that is only found in a certain area and nowhere else.

Endemic species are geographically restricted to a particular region, making them particularly vulnerable to habitat loss or environmental changes in that specific area, as they have no other populations elsewhere. Think of a local restaurant that only serves a dish unique to that town; that dish is 'endemic' to that town because you can't find it anywhere else.

ecosystem — A relatively self-contained, interacting community of organisms, and the environment in which they live and with which they interact.

An ecosystem includes both the living (biotic) components, such as plants, animals, and microorganisms, and the non-living (abiotic) components, such as soil, water, and air, all interacting as a functional unit. A fish tank is a small ecosystem: the fish, plants, and bacteria are the community, and the water, gravel, and filter are the environment they interact with.

community — All of the living organisms, of all species, that are found in a particular ecosystem at a particular time.

A community refers to the collection of different populations of species that live and interact within a specific area, forming a complex web of relationships such as predation, competition, and symbiosis. In a neighborhood, all the different types of people (families, individuals, different professions) living and interacting together form a community.

habitat — The place where an organism, a population or a community lives.

A habitat is the specific physical environment where a species or group of species naturally resides, providing the necessary resources and conditions for their survival and reproduction. Your home address is your habitat; it's the specific place where you live.

niche — The role of an organism in an ecosystem; it is how the organism ‘fits into’ the ecosystem.

An organism's niche describes its specific role, including how it obtains energy, its interactions with other species (e.g., predator, prey, competitor), and its relationship with the physical environment (e.g., temperature, light requirements). If a habitat is an organism's address, its niche is its job description, including what it eats, who eats it, and how it affects its surroundings.

species diversity — All the species in an ecosystem.

Species diversity considers both species richness (the number of different species) and species evenness (the relative abundance of each species). Higher diversity implies a greater number of species and a more balanced distribution of individuals among those species. Imagine two classrooms: one has 20 students, all from different countries (high species richness). Another has 20 students, with 19 from one country and 1 from another (low species evenness). Species diversity considers both.

genetic diversity — All the alleles of all the genes in the genome of a species.

Genetic diversity refers to the variation in genetic material (alleles) within a single species. This diversity is crucial for a species' ability to adapt to changing environmental conditions, resist diseases, and survive long-term. Think of a deck of cards for a species; genetic diversity is like having a full deck with many different suits and numbers (alleles), rather than a deck with only aces of spades.

random sampling — Method of investigating the abundance and/or distribution of populations which is determined by chance and shows no bias on the part of the person carrying out the sampling.

Random sampling ensures that every part of the study area has an equal chance of being sampled, thereby producing data that is representative of the entire area and minimizing observer bias. Picking names out of a hat to choose who gets a prize is random sampling; everyone has an equal chance, and the selection is unbiased.

quadrat — A square frame which is used to mark out an area for sampling populations of organisms.

Quadrats are used in ecological surveys to define a specific area for counting individuals, estimating percentage cover, or recording species frequency, particularly for sessile or slow-moving organisms. A quadrat is like a picture frame that you place on the ground to focus on and study a small, defined section of a larger landscape.

mark–release–recapture — A method of estimating the numbers of individuals in a population of mobile animals.

This technique involves capturing a sample of mobile animals, marking them, releasing them, and then recapturing a second sample to estimate the total population size. It assumes no immigration, emigration, births, or deaths between samples, and that marking does not affect survival or recapture probability.

systematic sampling — A non-random method of investigating the abundance and/or distribution of populations in which the position of sampling points are determined by the person carrying out the sampling (e.g. at every 2 m along a transect).

Systematic sampling is used when there is a clear environmental gradient or pattern in the distribution of species, allowing researchers to investigate how species abundance or distribution changes along that gradient. If you want to see how house prices change as you move away from the city center, you might check prices every mile along a straight road; this is systematic, not random.

transect — A line marked by a tape measure along which samples are taken, either by noting the species at equal distances (line transect) or placing quadrats at regular intervals (belt transect).

Transects are used in systematic sampling to study how species distribution and abundance change along an environmental gradient, such as from the seashore to inland, or up a mountain slope. They provide a structured way to record data at regular intervals.

Spearman’s rank correlation — A statistical test to determine if there is a correlation between two variables when one or both of them are not normally distributed.

Spearman's rank correlation coefficient (r_s) is a non-parametric measure of the strength and direction of association between two ranked variables. It is particularly useful when data are ordinal or when the assumptions for Pearson's correlation are not met.

Pearson’s linear correlation — A statistical test used to determine if there is a linear correlation between two variables that are normally distributed.

Pearson's linear correlation coefficient (r) measures the strength and direction of a linear relationship between two continuous variables. It requires that both variables are normally distributed and that the relationship is linear.

alien species — A species that has moved into a new ecosystem where it was previously unknown; also known as invasive species.

Alien species, also known as invasive species, can pose a significant threat to native biodiversity by outcompeting native species for resources, preying on them, or introducing diseases. Controlling these species is often necessary to protect local ecosystems.

assisted reproduction — Any technique that is involved in treating infertility or protecting a female mammal of an endangered species from the health risks of pregnancy.

Assisted reproduction techniques are vital in the conservation of endangered mammal species, helping to increase population numbers and maintain genetic diversity. These methods include artificial insemination, in vitro fertilisation, and embryo transfer.

artificial insemination (AI) — Injection of semen collected from a male into the uterus.

Artificial insemination is a technique used in assisted reproduction where semen is collected from a male and directly injected into the uterus of a female. This method can overcome geographical barriers or behavioral incompatibilities between individuals, facilitating breeding in endangered species.

in vitro fertilisation (IVF) — The fertilisation of an egg that occurs outside the body of a female (e.g. in a Petri dish).

In vitro fertilisation involves the fertilization of an egg by sperm outside the body, typically in a laboratory setting. The resulting embryos can then be transferred into a surrogate mother or cryopreserved for future use, offering a way to breed endangered species with limited reproductive success.

embryo transfer — Embryos are removed from the uterus of a female mammal of an endangered species shortly after fertilisation and transferred to surrogate females to bring to full term.

Embryo transfer involves moving embryos from a donor female to a surrogate mother. This allows a single endangered female to produce more offspring than she could naturally, as multiple surrogates can carry pregnancies to term, maximizing reproductive output.

surrogacy — A female becomes pregnant with an embryo from another female and carries it to full term; embryos can be conceived naturally, by AI or by IVF.

Surrogacy in conservation involves a female carrying an embryo from another female, often of an endangered species, to full term. This can be achieved through natural conception, artificial insemination, or in vitro fertilisation, providing a means to increase the birth rate of vulnerable populations.

frozen zoo — A facility where genetic materials taken from animals are stored at very low temperatures (–196 °C); sperm, eggs, embryos and tissue samples are examples of these genetic materials.

Frozen zoos are critical ex situ conservation facilities that store genetic material such as sperm, eggs, embryos, and tissue samples from endangered animals at ultra-low temperatures. This preserves genetic diversity for future breeding programs or reintroduction efforts, acting as a genetic safeguard against extinction.

seed bank — Facility where seeds are dried and kept in cold storage to conserve plant biodiversity.

Seed banks are vital for plant conservation, storing seeds under controlled conditions (dried and cold) to maintain their viability for long periods. This preserves the genetic diversity of plant species, including endangered ones and those with agricultural importance, for future use or reintroduction.

CITES — The Convention on International Trade in Endangered Species of Wild Fauna and Flora.

CITES is an international agreement that regulates the international trade of wild animals and plants to ensure that such trade does not threaten their survival. It lists species in appendices according to their level of threat, imposing varying degrees of control on their trade.

IUCN — The International Union for Conservation of Nature.

The IUCN is a global authority on the status of the natural world and the measures needed to safeguard it. It publishes the Red List of Threatened Species, which assesses the conservation status of species worldwide, guiding conservation action and policy.