Chapter 10 Flashcards
Why are organisms classified ?
To identify species by using a dearly defined system of classification. the species an organism belongs to can be easily identified. • To predict characteristics-if several members in a group have a specific characteristic, it is likely that another species in the group will have the same characteristic. • To find evolutionary links - species in the same group probably share characteristies because they have evolved from a common ancestor.
Order the classification system starting from kingdom
Kingdom Phylum Class Order Family Genus Species
How are organisms named binomially
The first word indicates the organism’s genus. It is called the generic name; you can think of this as being equivalent to your surname or family name, as it is shared by close relatives. The second word indicates the organism’s species. It is called the specific name.
What are the five kingdoms ?
Animalia , plantae , fungi , protoctista , prokaryotae.
What are the features of prokaryotae?
Unicellular
No nucleus and no membrane bound organelles.
Nutrients absorbed through wall or sometimes produced by photosynthesis.
Features of protoctista
Mainly unicellular
Have a nucleus and membrane bound organelles
Some have chloroplasts
Some are sessile but some move by cilia
Nutrients from digestion of other organisms and/or photosynthesis . Some a parasitic
Features of fungi
Uni and multi cellular Chitin cell wall Nucleus and membrane bound organelles No chloroplasts No movement Mycelium body Saprophytic feeders Food stored as glycogen
Features of plantae
Contain chloroplasts Cellulose cell wall Photosynthesis Food stored as starch Multicellular Most don’t move Nucleus and membrane bound organelles
Features of Animalia
Multicellular Can move No chloroplasts Nucleus and membrane bound organelles Food stored as glycogen Get food by ingestion
What is the structural difference between archaebacteria and eubacteria .
Eubacteria contain peptidoglycan in their cell walls whereas archaebacteria do not .
What is phylogeny?
Phylogeny is the name given to the evolutionary relationships between organisms. The study of the evolutionary history of groups of organisms is known as phylogenetics. It reveals which group a particular organism is related to, and how closely related these organisms are.
Phylogenetic trees
A phylogenetic tree (or evolutionary tree) is a diagram used to represent the evolutionary relationships between organisms. They are branched diagrams, which show that different species have evolved from a common ancestor. The diagram is similar in structure to that of a branching tree – the earliest species is found at the base of the tree and the most recent species are found at the tips of the branches.
Advantages of phylogeny
Phylogeny can be done without reference to Linnaean classification. Classification uses knowledge of phylogeny in order to confirm the classification groups are correct or causes them to be changed. For example, a dolphin has many of the same characteristics as a fish, so in theory a dolphin could be classified as a fish. However, knowledge of the phylogeny of dolphins confirms its classification as a mammal. Other advantages: • Phylogeny produces a continuous tree whereas classification requires discrete taxonomical groups. Scientists are not forced to put organisms into a specific grou that they do not quite fit. • The hierarchal nature of Linnaean classification can be misleading as it implies different groups within the same rank are equivalent. For example, the cats (Felidae) and the orchids (Orchidaceae) are both families. However, the two groups are not comparable – one has a longer history than the other (cats have existed for around 30 million years, but orchids have been in existence for over 100 million years). The two families also have different levels of diversity (with approximately 35 cat species and 20000 orchid species) and different degrees of biological differentiation (many orchids of different genera are able to hybridise, but cats cannot).
Evidence for evolution
palaeontology the study of fossils and the fossil record • comparative anatomy – the study of similarities and differences between organisms’ anatomy • comparative biochemistry – similarities and differences between the chemical makeup of organisms.
How do scientists determine how closely related species are
To discover how closely two species are related, the molecular sequence of a particular molecule is compared. (Scientists do this by looking at the order of DNA bases, or at the order of amino acids in a protein.) The number of differences that exist are plotted against the rate the molecule undergoes neutral base pair substitutions (which has been determined through studies). From this information scientists can estimate the point at which the two species last shared a common ancestor. Species that are closely related have the more similar DNA and proteins, whereas those that are distantly related have far fewer similarities. Ribosomal RNA has a very slow rate of substitution, so it is commonly used together with fossil information to determine relationships between ancient species
