classification and evolution Flashcards

You may prefer our related Brainscape-certified flashcards:
1
Q

classification of species

A

Taxonomy is the practice of biological classification

The biological classification system enables us to arrange species into groups based on their evolutionary origins and relationships

In this hierarchical system there is no overlap between groups and each group is called a taxon (plural taxa)

By grouping organisms into taxa it can make them easier to understand and remember

There are several different ranks or levels within the hierarchical classification system used in biology

Multiple smaller taxa can be put into one larger taxon

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

hierarchical classification

A

The hierarchical classification system of organisms in biology is used to organise and group similar organisms together so that they can be more easily understood

There are several taxonomic ranks that exist

All taxonomic ranks or ‘taxa’ make up a ‘taxonomic hierarchy’

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

taxonomic ranks

A

Species is the lowest taxonomic rank in the system

Similar species can be grouped in a genus (plural genera)

Similar genera can be grouped in a family

Similar families can be grouped into an order

Similar orders can be grouped into a class

Similar classes can be grouped into a phylum (plural phyla)

Similar phyla can be grouped into a kingdom

Similar kingdoms can be grouped into a domain

Domains are the highest taxonomic rank in the system

The first letters of all the different ranks below the domains can be remembered as:

Kings Play Chess On Fancy Gold Squares
Kittens Pounce Clumsily On Furry Green Spiders
Kingdom Phylum Class Order Family Genus Species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

eukarya

A

Eukarya is the domain of all eukaryotes, distinguishable from Bacteria and Archaea which are both prokaryotic domains

Just like the other domains, Eukarya contains the taxonomic hierarchy of kingdom, phylum, class, order, family, genus and species

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

binomial system

A

A species is a group of organisms that are able to reproduce to produce fertile offspring

Binomials are the scientific names given to individuals species

Binomials consist of the organism’s genus and species name in modern Latin

For example, the binomial for humans is Homo sapiens and the binomial for dogs is Canis familiaris

Binomials are extremely useful for scientists as they allow for species to be universally identified - the binomial for a species is the same across the entire globe

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

naming species

A

Species are often given common names, but these common names are often differ between countries and do not always translate directly between different languages

In order to avoid confusion about what group of organisms scientists are talking about, all species are given a two-part scientific name using the binomial system

This naming convention was developed and established by the Swedish scientist Carl Linnaeus in the 18th Century

The binomial name is always italicized in writing (or underlined if it is not possible to italicise)

The genus name should have a capital letter but the species name should not.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

classification of the three domain

A

Taxonomy is the practice of biological classification

It involves placing organisms into a series of categories or taxa

There are different ranks within the hierarchical classification system used in biology

The highest rank is the domain

There are three domains of life

Cell type has a major role in the classification of organisms into the three domains but do not confuse cell types and domains

The two cell types are prokaryotic cells and eukaryotic cells

Prokaryotic cells are easily distinguishable in that they lack a nucleus

Eukaryotic cells have compartmentalised structures, with at least their genetic material segregated from the rest of the cell in a nucleus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

the three domains of life

A

Although it was well known that most forms of life could be divided into prokaryotes and eukaryotes, advances in the studies of molecular biology, biochemistry and cell structure in the latter part of the 20th century showed that the prokaryotes are not one uniform group

Based on molecular analyses of RNA genes in particular, and by looking at features such as ribosomal RNA (rRNA), aspects of protein synthesis and the structure of cell membranes and flagella, scientists realised that using cell type to classify organisms was insufficient and that prokaryotes could be divided into two separate groups (domains)

The three domains are:
Bacteria (prokaryotes)
Archaea (prokaryotes)
Eukarya (eukaryotes)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

archaea

A

Organisms within this domain are sometimes referred to as the extremophile prokaryotes, as archaea were first discovered living in extreme environments (although not all archaea do)
Archael cells have no nucleus (and so are prokaryotic)

They were initially classified as bacteria until several unique properties were discovered that separated them from known bacteria, including:

Unique lipids being found in the membranes of their cells

No peptidoglycan in their cell walls

Ribosomal structure (particularly that of the small subunit) are more similar to the eukaryotic ribosome than that of the bacteria

Archaea have a similar size range as bacteria (and in many ways metabolism is similar between the two groups)

DNA transcription is more similar to that of eukaryotes

Example: Halobacterium salinarum is a species of the archaea domain that can be found in environments with high salt concentrations like the Dead Sea

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

bacteria

A

These are organisms that have prokaryotic cells which contain no nucleus

They vary in size over a wide range: the smallest are bigger than the largest known-viruses and the largest are smaller than the smallest known single-celled eukaryotes

Bacterial cells divide by binary fission

Example: Staphylococcus pneumoniae is a species of bacteria that causes pneumonia

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

eukarya

A

Organisms that have eukaryotic cells with nuclei and membrane-bound organelles are placed in this domain

They vary massively in size from single-celled organisms that are only several micrometres across, to large multicellular organisms many-metres in size, such as blue whales

Eukaryotic cells divide by mitosis

Eukaryotes can reproduce sexually or asexually

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Key differences between archaea & bacteria

A

Initially, all organisms within the Archaea domain were classified as Bacteria

Then several unique features possessed by Archaea were discovered that separated them from both Bacteria and Eukarya

The main differences between Archaea and Bacteria are seen in:
Membrane lipids
Ribosomal RNA
Cell wall composition

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

membrane lipids

A

The membrane lipids found in the cells of Archaea organisms are completely unique

They are not found in any bacterial or eukaryotic cells

The membrane lipids of Archaea consist of branched hydrocarbon chains bonded to glycerol by ether linkages

The membrane lipids of Bacteria consist of unbranched hydrocarbon chains bonded to glycerol by ester linkages

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

ribosomal RNA

A

Both Archaea and Bacteria possess 70S ribosomes
The 70S ribosomes in Archaea possess a smaller subunit that is more similar to the subunit found in Eukaryotic ribosomes than subunits in Bacterial ribosomes

The base sequences of ribosomal RNA in Archaea show more similarity to the rRNA of Eukarya than Bacteria

The primary structure Both Archaea and Bacteria possess 70S ribosomes

The 70S ribosomes in Archaea possess a smaller subunit that is more similar to the subunit found in Eukaryotic ribosomes than subunits in Bacterial ribosomes

The base sequences of ribosomal RNA in Archaea show more similarity to the rRNA of Eukarya than Bacteria

The primary structure of ribosome proteins in Archaea show more similarity to the ribosome proteins in Eukarya than Bacteria of ribosome proteins in Archaea show more similarity to the ribosome proteins in Eukarya than Bacteria

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

composition of cell walls

A

Organisms from the Bacteria domain have cells that always possess cell walls with peptidoglycan

Organisms from the Archaea domain also have cells that always possess cell walls, however these do not contain peptidoglycan

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

classification of the five kingdoms

A

Before the three domains of life (Bacteria, Archaea and Eukarya) were introduced and then widely accepted as the highest rank in the classification of life on Earth, most people thought there to be five kingdoms at the top of the classification hierarchy

These five kingdoms include:
Prokaryota
Protoctista
Fungi
Plantae
Animalia

17
Q

prokaryota

A

This kingdom includes bacteria and blue-green bacteria
The main features of all organisms within Prokaryota include:

Most are unicellular (some can be found as filaments of cells or groupings of similar cells known as colonies)

Their cells have cell walls (not made of cellulose) and cytoplasm but no nucleus or mitochondria

They vary in size over a wide range: the smallest are bigger than the largest known viruses and the largest are smaller than the smallest known single-celled eukaryotes
Their cells divide by binary fission

Blue-green bacteria and some bacteria are autotrophic (they are photosynthetic)

Many bacteria are heterotrophic (feeding by decomposing living or dead organic materials)

18
Q

kingdom protoctista

A

All Protoctista are eukaryotic, and this broad group of cellular life encompasses all eukaryotic cells that do not belong to the other three eukaryotic kingdoms

Members of this kingdom show great diversity in all aspects of life including structure, life cycle, feeding and trophic levels and well as modes of locomotion

Protoctists can exist as single-celled organisms or as a group of similar cells

A group of Protoctista known as protozoa possess cells similar to animal cells
Their cells have no cell wall

Another group of Protoctista known as algae possess cells similar to plant cells

Their cells have cellulose cell walls and chloroplasts

19
Q

kingdom fungi

A

All fungi are eukaryotic cells
The cells of fungi:
- Possess non-cellulose cell walls (often made of the polysaccharide chitin)
- Don’t have cilia
- Fungi are heterotrophs:

They use organic compounds made by other organisms as their source of energy and molecules for metabolism

They obtain this energy and carbon by digesting dead/decaying matter extracellularly or from being parasites on living organisms

Fungi reproduce using spores that disperse onto the ground nearby

Fungi have a simple body form:
They can be unicellular (like the common baker’s yeast Saccharomyces cerevisiae

Some consist of long threads called hyphae that grow from the main fungus body and form a network of filaments called the mycelium

Larger fungi possess fruiting bodies that release large numbers of spores (this is how many fungi reproduce)

20
Q

kingdom plantae

A

Plants are multicellular eukaryotic organisms
Plant cells:

All have cell walls composed of cellulose

Possess large (and usually permanent) vacuoles that provide structural support

Are able to differentiate into specialized cells to form tissues and organs

Possess chloroplasts that enable photosynthesis (not all plant cells have chloroplasts)

Can sometimes have flagella

They are autotrophs
This means they can synthesize their organic compounds and molecules for energy use and building biomass from inorganic compounds

Plants have complex body forms

They have branching systems above and below the ground

21
Q

kingdom animalia

A

Animals are also multicellular eukaryotic organisms

Animal cells:

Are able to differentiate into many different specialised cell types that can form tissues and organs

Have small temporary vacuoles (for example, lysosomes)

Have no cell walls

Sometimes have cilia

They are heterotrophs and have a wide range of feeding mechanisms

Communication within their complex body forms takes place through a nervous system and chemical signalling