Chapter 10 Classification and Evolution Flashcards
(23 cards)
What is a classification system?
A process by which living organisms are sorted into groups. The organisms will share similar features.
What was the most used classification system
Seven groups are ordered in a hierarchy. These are known as taxonomic groups: Kingdom, Phylum, Class, Order, Family, Genus, Species.
Kingdoms are the largest and cover the most organisms whereas Species cover the least.
Why do scientists classify organisms?
To identify species - by using a clearly 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 characteristics.
To find evolutionary links - species in the same group probably share characteristics because they have evolved from a common ancestor.
How are organisms classified?
First the organisms are separated into 3 domains - Archae, Bacteria, Eukarya. As you move down the levels there are more groups at each level and organisms become more similar. It ends with individual species being named.
What is a species?
A group of organisms that are able to reproduce to produce fertile offspring.
e.g. Donkeys reproduce with donkeys making donkeys which are fertile. Horses reproduce with horses which make horses that are fertile. But Horses reproducing with Donkeys produces mules which are infertile. Therefore horses and donkeys are species but mules arent.
Why are mules and hinnies infertile
Because their cells contain an odd number of chromosomes. This means that meiosis and gamete production cannot take place correctly as all chromosomes must pair up.
Classification of humans
Humans belong to a species named homo sapiens.
Naming - Common names
Before classification was used, many organisms were given names based on their physical characteristics, behaviour or habitat. e.g. blackbirds - colour, song thrushes - songs, fieldfares - habitat.
Why was naming by common names not efficient
the names would have different translations in other languages and may have other common names.
Common names also don’t provide relationships between organisms. e.g. the blackbirds, song thrushes, and fieldfares all belong to the genus Turdus so they are all from the same ancestor, but you wouldn’t know this from their common names, not from characteristics.
Naming - binomial nomenclature
This method makes all scientists across the world at the same playing field. It was developed by Carl Linnaeus.
All species are give a scientific name consisting of two parts:
- the first word indicates the organisms genus. It is the generic name.
- the second word indicates the organisms species. It is called the specific name.
These words should be written in italics. Since it is difficult to write in italics it is standard procedure to underline.
First letter of genus should be in capital.
What are the five kingdoms?
Prokaryotae - bacteria
Protoctisa - unicellular eukaryotes
Fungi - yeast, moulds, mushrooms
Plantae - the plants
Animalia - animals
Prokaryotae
- Unicellular
- No nucleus or other membrane-bound organelles - a ring of naked DNA - small ribosomes.
- no visible feeding mechanism - nutrients are absorbed through the cell wall or produced internally by photosynthesis.
Proctoctista
- mainly unicellular
- a nucleus and other membrane-bound organelles
- some have chloroplasts
- some are sessile, but others move by ciliua, flagella or amoeboid mechanisms.
- nutrients are acquired by photosynthesis ( autotrophic feeders), ingestion of other organisms (heterotrophic feeders), or both some are parasitic,.
Fungi
- Unicellular or multicellular
- a nucleus and other membrane bound organelles and a cell wall mainly composed of chitin.
- no chloroplasts or chlorophylll
- no mechanisms for locomotion
- most have a body of mycelium made of threads or hyphae
- nutrients are acquired by absorption - mainly from decaying material - they are saprophytic feeders - some are parasitic
- most store their food as glycogen
Plantae
- multicellular
- a nucleus and other membrane-bound organelles including chloroplasts, and a cell wall mainly composed of cellulose
- all contain chlorophyll
- most do not move, although gametes of some plants move using cilia or flagella
nutrients are acquired by photosynthesis - they are autotrophic feeders - organisms that make their own food - store food as starch.
Animalia
- multicellular
- a nucleus and other membrane-bound organelles
- no chloroplasts
- move with the aid of cilia, flagella or contractile proteins, sometimes in the form of muscular organs
- nutrients are acquired by ingestion - they are hetertrophic feeders
- food stored as glycogen
Are there now six kingdoms?
The current system used is called the three domain system.
Woese came up with this system by investigating differences in the sequences of nucleotides in the cells RNA, as well as the cells membrane lipid structure and their sensitivity to antibiotics.
The 3 domains are Archae, Bacteria, and Eukarya. The organisms in the different domains contain a unique form of rRNA and different ribosomes.
Eukarya - 80s ribosomes, RNA polymerase has 12 proteins
Archae - 70s ribosomes, RNA polymerase has 8-10 proteins
Bacteria - 70s ribosomes, RNA polymerase has 5 proteins
What happened to prokaryotae from 5 kingdom system to the 6 kingdom
Prokaryotae kingdom has been broken down into archaebacteria and eubacteria. This is because there were chemical difference in the makeup of archaebacteria and eubacteria. e.g. eubacteria contain a peptidoglycan cell wall whereas archaebacteria do not.
What are archaebacteria
They live in extreem environments. This includes thermal vents, anaerobic conditions and highly acidic environments. e.g. methanogens live in anaerobic environments such as sewage treatment plants and make methane.
What are eubacteria
are found in all environments and are the common bacteria
Why is phylogeny?
It’s the name given to evolutionary relationships between organisms. The study of this is called phylogenetics. It reveals how closely related organisms are.
Phylogenetic trees
its a diagram used to show evolutionary relationships. They are branched diagrams which show that different species have evolved from a common ancestor.
The earliest species are found at the base of the tree and the most recent are found at the tips of the branches.
Advantages of phylogenetic classification
Phylogeny can be done without reference to linnaean classification.
Phylogeny produces a continuous tree whereas classification requires discrete taxonomical groups.
The hierarchical nature of linnaean classification can be misleading as it implies different groups within the same rank are equivalent.
