Chapter 2 - Biodiversity and Classification

. To qualify as one of the world’s biodiversity hotspots, an area must:

1 contain at least 1500 species of endemic vascular plants found nowhere else on Earth

2 have lost at least 70% of its primary native vegetation

Gene

A section of DNA in a chromosome that encodes an instruction, usually for a specific protein, which, when expressed, may affect a certain characteristic. Genes are inherited by offspring. Genes can come in different forms. A higher number of different forms of a gene in one species constitutes a higher genetic diversity for that species.

Gene pool

The sum of all the genes, including all of their different forms, in a given population of one species; sometimes, it is also used to refer to all the genes in a species

Species

A group of morphologically similar organisms that share a gene pool; members of the same species are able to interbreed under natural conditions to produce viable and fertile offspring.

Ecosystem

All the organisms in a particular area, along with the non-living components of their environment, and all their interactions. It is a self-sustaining unit. Ecosystems can vary greatly, depending on biotic and abiotic factors.

Biosphere

All the environments on Earth that organisms inhabit; the combined sum of Earth’s ecosystems.

the biological species concept

In biological terms, a species is a group of organisms who are able to interbreed in nature and produce viable, fertile offspring.

How is all life on earth connected

through the cycling of nutrients and the transformation of energy through food webs. It tends to be assumed that an ecosystem has some level of isolation from other ecosystems, meaning that more materials are cycled and transferred within an ecosystem than between one ecosystem and another. In reality, materials do cross the boundaries separating one ecosystem from another. For example, a predator such as the Australian dingo may have a range that crosses a number of different ecosystems. Different ecosystems provide specialised habitat for different sets of species adapted to their unique combination of biotic and abiotic factors. This largest scale of biological diversity is important in maintaining species and genetic diversity.

Spatial scales

Spatial refers to the space being occupied. Scientists study spatial patterns to understand the extent (size of an area) and distribution of all the individuals in a species (the species biodiversity). Distribution is the location-pattern of members of a species in an area; in other words, where individuals of the same classification group are distributed in an area. The distribution of individuals can be observed in patterns

Terrestrial

Terrestrial ecosystems are those on dry land and aquatic ecosystems are those in water.

Temporal scales

Temporal refers to time. Temporal patterns are studied to provide details about biodiversity in a certain area over a certain time period. Studies may be over time frames varying from geological periods (prehistoric to modern day), to seasons, to generations.

Scientists study and measure the biodiversity of organisms, including

including spatial (how organisms are distributed over space) and temporal (how organisms are distributed over time; e.g. day, year) patterns.

Why classify organisms?

Classification of organisms is important for several reasons. First, the diversity of life on Earth is so enormous that classifying organisms is a way of organising information. This allows us to see patterns and trends, and to better understand relationships between organisms. So, the second reason to classify organisms is to allow biologists to analyse information about organisms. Classification systems enable data collection, comparison and evaluation. The third reason is that classifying organisms allows biologists to communicate with one another. Because classification systems are standard worldwide, biologists can identify organisms that have already been discovered and more accurately compare their findings with one another, enabling international collaboration. Finally, classification means invasive species can be identified more easily and accurately. Classification reduces the risk of confusing an invasive species with an endangered species.

taxa or taxonomic levels

Scientists classify organisms into a number of groups that form a hierarchy or series of nested levels.

Initially, organisms are classified into very large groups called

domains.

phylum

Organisms within a phylum can be further grouped according to similar features. These smaller groupings are called classes.

Organisms are classified into a hierarchy of groups called taxa. The names of the taxa are

domain, kingdom, phylum, class, order, family, genus and species.

There are four kingdoms in Domain Eukarya

Animalia, Plantae, Protista and Fungi

Kingdom Animalia

contains all of the animals.

Plants (Kingdom Plantae)

obtain energy from the Sun using organelles called chloroplasts, and their cells have cell walls that contain cellulose.

Kingdom Fungi

Yeasts, mushrooms and moulds all belong to Kingdom Fungi and are characterised by having cell walls made of a specific polysaccharide (chitin)

The protists (Kingdom Protista

are a diverse group of organisms that are mostly single-celled and live in aquatic environments.

In the binomial system for naming species:

• the genus name has the first letter capitalised

• the species name is not capitalised

• when hand written, they are underlined; for example, Homo sapiens

• when in print, they are in italics; for example, Homo sapiens

Classification is based on

the idea that members of the same group share characteristics that are not present in members outside the group

Eutherian

(or placental) mammals give birth to live young after a gestation period during which the foetus develops inside the mother.

Marsupials

give birth to live young at a very early developmental stage. These young then develop in a pouch on the belly of the mother until they are mature enough to survive outside.

Monotremes

are the very small group of mammals that lay eggs

Animals are a kingdom of consumers. They are

multicellular heterotrophic eukaryotes that are classified based on their body plans and developmental pathways. Their classification is fundamentally related to their phylogeny (i.e. evolutionary ancestry), morphology (i.e. structure) and, due to advancements in biotechnology, molecular data (i.e. DNA and proteins).

The animal kingdom is classified into

36 recognised animal phyla, of which nine (Mollusca, Porifera, Cnidaria, Platyhelminthes, Nematoda, Annelida, Arthropoda, Echinodermata and Chordata) contain the vast majority of known living species (Figure 2.19).

The five main classes of Chordata share the

morphological features of having a dorsal nerve cord and notochord, as well as some features in the embryo that may persist into adulthood.

members of Kingdom Plantae are

terrestrial plants

Plants are autotrophic; that is,

they produce their own simple sugars through photosynthesis.

Plants are first classified into two groups according to

whether or not they have vascular tissue.

Vascular tissue

is comprised of phloem and xylem, which are tubes of connected cells that transport nutrients and water through the plant.

. Vascular plants include

angiosperms, gymnosperms and ferns (also called pteridophytes).

Non-vascular plants are called

bryophytes, and include liverworts and mosses.

Bryophytes

are photosynthetic, but, since they lack vascular tissue, water moves through them by osmosis.

plants evolved vascular tissue

able to transport more water at a faster rate and therefore became able to grow larger.

seed

A seed is an embryo with a stored food supply.

Gymnosperms

are non-flowering plants which have both male and female sex cells (gametophytes) in cones

are non-flowering plants which have both male and female sex cells (gametophytes) in cones

(flowering plants) have male and female sex cells (gametes) in parts of the flower. When angiosperms first germinate they produce one of two types of cotyledon (embryonic leaf). This feature is used to further classify angiosperms into groups called monocotyledons and dicotyledons.

Classification key

are tools used by scientists to identify organisms that belong to species that have already been discovered. Using information about the physical features and habitats of organisms, classification keys guide scientists through the identification process of, for example, an Australian sea snail.

Starting of classification key

At the start of a classification key the user is given a choice between several options, one of which describes the organism to be identified. Each choice leads to more options to choose between. The user continues to make choices until they reach an endpoint

Most classification keys are dichotomous,

meaning that at each step the user has to choose between two options.

Class Aves and Class Mammalia are

clades because they contain all of the animals on that branch. Class Reptilia, however, is not a clade. This is because it does not contain birds, which also descended from a reptilian ancestor.

Class Reptilia

can be called a paraphyletic group. This arrangement has occurred because birds and reptiles were classified into separate classes before their evolutionary relationships were known.

cladograms represent

theories about the way that organisms are related.