2.1- All organisms are related through their evolutionary history Flashcards
(a)
Classification
Classification groups organisms based on evolutionary relationships. It’s hierarchical (large groups split into smaller ones) and phylogenetic (organisms in the same group are closely related). Each group is a taxon, and organisms can only belong to one group at each taxonomic level, making it discrete.
(b)
The need for classification and its tentative nature
Classification is based on current information and can change with new discoveries. For example, in 2020, DNA analysis showed there are four species of Gentoo penguins, not one. This shows classification is tentative and constantly revised as new evidence emerges.
(c)
Domain classification system
Eubacteria, Archea, Eukaryota
(c)
Kingdom
classification system
Prokaryotae, Animalia, Plantae, Fungi, Protoctista
(d)
Characteristics of prokaryotae
Lack a nucleus and membrane-bound organelles, have 70S ribosomes, circular DNA and a cell wall of
peptidoglycan.
(d)
Characteristics of Protoctista
Mostly unicellular eukaryotes, algae have no tissue differentiation
(d)
Characteristics of Plantae
Multicellular eukaryotes, photosynthetic containing chloroplasts, have a cell wall of cellulose
(d)
Characteristics of Fungi
Heterotrophic eukaryotes with a cell wall made of chitin; most are composed of thin threads called hyphae, reproduce by spores
(d)
Characteristics of Animalia
Multicellular eukaryotes, no cell wall, heterotrophic and have nervous co-ordination
(e)
Homologous structures
Structures in different species with a similar anatomical position and development origin, derived from a common ancestor.
(e)
Pentadactyl
Having five digits.
(e)
Divergent evolution
The development of different structures over long period of time, from the equivalent structures in related organisms.
(e)
Convergent evolution
The development of similar features in unrelated organisms over long periods of time, related to natural selection of similar features in a common environment.
(e)
Analogous structures
Have a corresponding function and similar shape, but have a different developmental origin.
(e)
Assessing relatedness with genetic evidence - DNA sequence
DNA sequences change over time, accumulating differences between species. Closely related species have more similar DNA than distantly related ones. DNA analysis confirms evolutionary relationships and corrects errors in classification based on physical traits.
(e)
Assessing relatedness with genetic evidence - DNA hybridisation
DNA hybridisation compares DNA base sequences between species by mixing single-stranded DNA fragments. Complementary sequences hybridise, showing genetic similarity. For example, humans and chimpanzees share at least 95% of their DNA, while humans and rhesus monkeys share about 93%. This method reveals evolutionary relationships, such as the close link between hippos and whales.
(e)
Assessing relatedness with genetic evidence - Amino acid sequences
Amino acid sequences in proteins reflect the DNA base sequence. Similarity in these sequences shows how closely related species are. For example, differences in fibrinogen amino acid sequences have been used to propose an evolutionary tree for mammals.
(e)
Assessing relatedness with genetic evidence- Immunology
Immunological techniques compare proteins between species. When antigens (e.g., albumin) of one species mix with antibodies of another, coagulation occurs. Greater coagulation indicates a closer evolutionary relationship.
(f)
Species
A group of organisms with similar characteristics that can interbreed to produce fertile offspring.
(g)
The use of the binomial system in naming organisms
All species have a binomial name consisting of two parts: the generic name (genus), which is capitalised, and the species name, which is in lowercase. Organisms in the same genus are more closely related than those in different genus. Binomial names are written in italics to follow convention and are universally recognised, preventing confusion from local names and language differences.
(h)
Biodiversity
Biodiversity refers to the number of different species (species richness) and the number of individuals of each
species (species evenness) in a given environment.
(i)
Biodiversity varying spatially and temporally
Biodiversity varies spatially – the closer to the equator, the
more biodiversity there is.
Biodiversity varies temporally – through time biodiversity
has varied, e.g. mass extinctions reduce biodiversity.
(i)
Factors affecting biodiversity
Sucession
Natural selection
Human influence
(j)
Simpson’s Diversity Index
Simpson’s diversity index reduces species richness and evenness to a single number so that different areas can be compared.
