Topic 4.5 Species & Taxonomy Flashcards
(22 cards)
What is a species?
A group of similar organisms that can breed together to produce living, fertile offspring
Why must species be genetically similar?
This is so the genes of one individual can combine with the genes of another in sexual reproduction
Hybrids are always…
sterile. They cannot form gametes in meiosis as chromosomes don’t form homologous pairs
What is courtship behaviour?
The behaviour by which different species identify, attract and select partners for reproduction
What is a taxon?
A group of organisms
What is the taxon hierarchy?
Domain - Kingdom - Phylum - Class - Order - Family - Genus - Species
Why is it difficult defining species?
• Species evolve/change over time
• Many species are now extinct
• There is lots of genetic variation within species
• There may be reproductive isolation, so different groups of the same species never meet or interbreed
• Some species only reproduce asexually (eg. bacteria)
Why is courtship behaviour important?
It is genetically determined, has evolved and therefore increases chance of survival.
It maximises chance of successful mating and offspring survival
What does courtship behaviour enable individuals to do?
- Recognise members of their own species
- Identify a mate capable of breeding
- Form a pair bond
- Synchronise mating
- Become able to breed
What are the 3 domains?
Archae - very ancient prokaryotic microbes
Eubacteria - more advanced prokaryotic microbes
Eukaryotes- all life forms with eukaryotic cells (plants and animals)
What is the binomial nomenclature?
A universal system for naming organisms.
First word is Genus, second word is species.
Written in italics or underlined if handwritten
What is a phylogenetic tree?
A branching diagram showing the evolutionary relationships between different species
What does a phylogenetic tree show?
How long ago two species shared a common ancestor and how closely related they are
What is artificial classification?
Based on non-evolutionary, physical features (size, colour, number of limbs/leaf)
Why is artificial classification misleading?
Similar structures may perform the same function but have different evolutionary origins
Q. What is phylogenetic classification?
Based on evolutionary, anatomical features between organisms and their ancestors. These features have the same basic design so must have been present in a common ancestor
How does mRNA sequencing provide evidence for phylogenetic trees?
• mRNA base sequences are formed from the DNA base sequence but only includes exons. This provides information on the functional part of the genome
• mRNA is shorter and doesn’t contain introns so there is much less data to analyse
Q. What evidence can be used to construct phylogenetic trees?
DNA Sequencing
mRNA sequencing
Comparing amino acid sequences
Immunological comparison
How can amino acid sequences be compared to provide evidence for phylogenetic trees?
Amino acid sequences are direct products of gene expression, providing data on functional part of the genome.
Q. How does DNA sequencing work?
Entire base sequences of the genome of an organism can be determined and compared with another organism.
Closely related species share a higher % similarity in DNA base order
What are the steps in immunological comparisons?
- Human blood serum injecting into rabbit. Rabbit forms antibodies that identify & attach to human blood proteins and render them harmless
- Sample taken from rabbits blood and anti-human antibodies extracted
- These antibodies are added to blood samples of other species to see how well they recognise human blood proteins.
More similar blood = more reactions = more precipitate forms
What are the benefits and disadvantages of using amino acid sequences for phylogenetic trees?
+ doesn’t include non coding regions
- detail is lost (degenerate code means same AA sequence could have different mRNA base sequence)
