Classification and Evolution Flashcards
What is classification?
Classification is the act of arranging organisms into groups based on their similarities and differences.
This makes it easier for scientists to identify them and to study them. Taxonomy is the study of classification. There are a few different classification systems in use, but they all involve placing organisms into groups in a taxonomic hierarchy:
1) There are eight levels of groups (called taxonomic groups) used in classification.
2) Similar organisms are first sorted into one of three very large groups called domains, e.g. animals, plants and fungi are in the Eukarya domain. 3) Similar organisms are then sorted into slightly smaller groups called kingdoms, e.g. all animals are in the animal kingdom. 4) Similar organisms from that kingdom are then grouped into a phylum. Similar organisms from each phylum are then grouped into a , and down the eight levels of the taxonomic hierarchy.
5) As you move down the hierarchy, there are more groups at each level but fewer organisms in each group.
6) The hierarchy ends with species — the groups that contain only one type of organism (e.g. humans, dog, E. coli and about 50 million other living species).
What are the 8 levels of the taxonomic hierarchy?
Domain Kingdom Phylum Class Order Family Genus Species
How many kingdoms are there?
5
What are the 5 kingdoms?
Prokaryotae Protoctista Fungi Plantae Animalia
What is an example of Prokaryotae and its features?
prokaryotic, unicellular (single-celled),
no nucleus, less than 5 µm
bacteria
What is an example of Protoctista and its features?
eukaryotic cells, usually live in water, single-celled
or simple multicellular organisms
algae, protozoa
What is an example of Fungi and its features?
eukaryotic, chitin cell wall, saprotrophic (absorb
substances from dead or decaying organisms),
single-celled or multicellular organisms
moulds, yeasts,
mushrooms
What is an example of Plantae and its features?
can photosynthesise, contain chlorophyll,
autotrophic (produce their own food)
mosses, ferns,
flowering plants
What is an example of Animalia and its features?
nematodes (roundworms),
molluscs, insects, fish,
reptiles, birds, mammals
eukaryotic, multicellular, no cell walls,
heterotrophic (consume plants and animals)
Why Is The Binomial Naming System is Used in Classification
1) The nomenclature (naming system) used for classification is called the binomial system
— all organisms are given one internationally accepted scientific name in Latin that has two parts.
2) The first part of the name is the genus name and has a capital letter. The second part is the species
name and begins with a lower case letter. E.g. using the binomial system humans are Homo sapiens.
Names are always written in italics (or they’re underlined if they’re handwritten).
3) The binomial system helps to avoid the confusion of using common names. E.g. over 100 different
plant species are called raspberries and one species of buttercup has over 90 different common names.
What is Phylogeny?
1) Phylogeny is the study of the evolutionary history of groups of organisms. Phylogeny tells us who’s related to whom and how closely related they are. 2) All organisms have evolved from
shared common ancestors (relatives). This can be shown on a
phylogenetic tree, 3) This tree shows the relationship
point between members of the Hominidae family (great apes and humans). The first branch point represents a common ancestor of all the family members. This ancestor is now extinct. Orangutans were the first group to diverge (evolve to become a different species) from this common ancestor. 4) Each of the following branch points represents another common ancestor from which a different
group diverged. Gorillas diverged next, then humans, closely followed by bonobos and chimpanzees. 5) According to phylogenetics, a species is the smallest group that shares a common ancestor — in other words, the end of a branch on a phylogenetic tree. 6) Closely related species diverged away from each other most recently. E.g. humans and chimpanzees are closely related, as they diverged very recently. You can see this because their branches are close together. Humans and orangutans are more distantly related, as they diverged longer ago, so their branches are further apart.
Classification Systems are now Based on a?
Classification Systems are now Based on a Range of Evidence
Why Observable Features aren’t Always Enough?
1) Early classification systems only used observable features (things you can see) to place organisms into groups, e.g. whether they lay eggs, can fly or can cook a mean chilli... 2) But this method has problems. Scientists don’t always agree on the relative importance of different features and groups based solely on physical features may not show how related organisms are.
How does Other Evidence Shows How Similar Organisms are
Other Evidence Shows How Similar Organisms are
1) Classification systems are now based on observable features along with other evidence.
2) The more similar organisms are, the more related they are. We now use a wide range of evidence
to see , and therefore how related, organisms are.
Why Does New Technology Means New Discoveries
New Technology Means New Discoveries
1) New technologies (e.g. new DNA techniques,
better microscopes) can result in new
discoveries being made and the relationships
between organisms being clarified.
2) Scientists can share their new discoveries in
meetings and scientific journals (see p. 2).
How organisms are classified is continually
revised to take account of any new findings
that scientists discover.
What is Five Kingdoms Vs Three Domains?
Five Kingdoms Vs Three Domains
The five kingdom classification system has now been replaced with the three domain system
What is the 3 domain system?
1) In the older system the largest groups were the five kingdoms — all
organisms were placed into one of these groups. 2) In 1990, the three domain system was proposed. This new system has three domains — large super kingdoms that are above the kingdoms in the taxonomic hierarchy. 3) In the three domain system, organisms that were in
the kingdom Prokaryotae (which contains unicellular organisms without a nucleus) are separated into two domains — the Archaea and Bacteria. 4) Organisms with cells that contain a nucleus are placed in the domain Eukarya (this includes four of the five kingdoms). 5) The lower hierarchy stays the same — Kingdom, Phylum, Class, Order, Family, Genus, Species.
How Did Molecular Evidence Led to the Proposal of the Three Domain System
Molecular Evidence Led to the Proposal of the Three Domain System
1) The three domain system was proposed because of new evidence, mainly molecular. E.g. the Prokaryotae were reclassified into two domains because new evidence showed large differences between the Archaea and Bacteria. The new evidence included: Molecular evidence — The enzyme RNA polymerase (needed to make RNA) is different in Bacteria and Archaea. Archaea, but not Bacteria, have similar histones (proteins that bind to DNA) to Eukarya.
• Cell membrane evidence — The bonds of the lipids in the cell membranes of Bacteria and Archaea are different. The development and composition of flagellae are also different. 2) Most scientists now agree that Archaea and Bacteria evolved separately and that Archaea are more closely related to Eukarya than Bacteria. The three domain system reflects how different the Archaea and Bacteria are.
3) The development of the three domain system is an example of how scientific knowledge is always changing and improving
What is variation?
Variation is the differences that exist between individuals. Every individual organism is unique — even clones (such as identical twins) show some variation.
What 2 ways can variation occur?
Within a species
between a species
What is variation within a species?
1) Within species —Variation within a species is called intraspecific variation. For example,individual European robins weigh between 16 g and 22 g and show some variation in many other characteristics including length, wingspan, colour and beak size.
Whats variation between species?
2) Between species — The variation between different species is called interspecific variation. For example, the lightest species of bird is the bee hummingbird, which weighs around 1.6 g on average. The heaviest species of bird is the ostrich, which can weigh up to 160 kg (100 000 times as much).
What is continuous variation?
Continuous variation is when the individuals in a population vary within a range — there are no distinct categories, e.g. humans can be any height within a range (139 cm, 175 cm, 185.9 cm, etc.), not just tall or short.
Here are some more examples: are not distinct
Animals
1) Milk yield — e.g. cows can produce any volume of milk within a range. 2) Mass — e.g. humans can be any mass within a range.
Plants
1) Number of leaves — e.g. a tree can have any number of leaves within a range. 2) Mass — e.g. the mass of the seeds from a flower head varies within a range.
Microorganisms
1) Width — e.g. the width of E. coli bacteria varies within a range.
2) Length — e.g. the length of the flagellum can vary within a range.
Whats discontinuous variation?
Discontinuous variation is when there are two or more distinct
categories — each individual falls into only one of these
categories, there are no intermediates. Here are some examples:
Animals Blood group
Plants
1) Colour — e.g. courgettes are either yellow, dark green or light green. 2) Seed shape — e.g. some pea plants have smooth seeds and some have wrinkled seeds.
Microorganisms
1) Antibiotic resistance — e.g. bacteria are either resistant or not.
2) Pigment production — e.g. some types of bacteria can produce a coloured pigment, some can’t.
