Classification, biodiversity, evolution Flashcards
What is the binomial system, phylogeny and classification
BINOMIAL SYSTEM
-system that uses the genus name and species to avoid confusion when naming organisms
PHYLOGENY
-study of evolutionary relationships
CLASSIFICATION
-process of placing living things into groups
Why do we classify living things
-for our convenience
-to make study of living things manageable
-easier to identify organisms
-helps us see relationships between species
List the 8 taxonomic levels in classification
DOMAIN- domain is the highest taxonomic rank
-there are three domains, Archaea, Eubacteria and Eukaryote
KINGDOM- traditionally 5 main kingdoms; plantae, animalia, fungi and proctista are all eukaryotes which possess a nucleus
-all single celled organisms that do not possess a nucleus are grouped into kingdom prokaryote
PHYLUM- major subdivision of the kingdom
-a phylum contains all groups of organisms that have same body plan - e.g. possession of a backbone
CLASS- group of organisms that all possess the same general traits -e.g. same number of legs
ORDER- subdivision of class using additional information about the organism e.g. class mammal divided into meat eating (carnivore) or vegetation eating animals (herbivora)
FAMILY- group of closely related genera e.g. within order carnivora we might recognise the dog family and cat family
GENUS- group of closely related species
SPECIES- basic unit of classification
-all members of species show some variation but essentially same
Describe classifying species
-at higher levels of ranked system, differences between the organisms can be very great
-therefore quite easy to place a species into its domain, kingdom or phylum
-within phylum, species must be placed in a class
-this becomes more difficult as differences between classes in one phylum may not be very great
-as you descend to lower taxonomic groups it becomes increasing difficult to separate closely related species and to place a species accurately
-a more and more detailed description of the species is required
What is the binomial naming system
-binomial means 2 names
-binomial system of naming organisms; the genus name and the species name are used
-thus humans become Homo sapies
-the genus name always given a capital whilst the species given a lowercase
Who devised the binomial system
-made up by Carl Linnaeus
-before this a common name was used however it doesn’t work well because:
-some organism may have completely different common name in different parts of one country
-different common names used in different countries
-translation of languages or dialects may give different names
-same common name may be used for different species in other parts of the world
-Linnaeus used Latin as universal language
-this means whenever a species is named, its given a universal name
-every scientist in every country uses same name, avoiding confusion
Features of classification
1) observable features
2) better, more detailed evidence e.g. microscopes
3) best, DNA/RNA/ proteins
Define autotroph, photoautotroph, chemoautotroph and heterotroph
AUTOTROPH- organism that can make its on organic molecules from simple inorganic molecules
PHOTOAUTOTROPH- use light energy as food to make food
CHEMOAUTOTROPH- use chemicals to make food
HETEROTROPH- organism that requires ready made source of organic molecules
Describe animalia
-eukaryotic, multicellular
-heterotrophic
-usually able to move around
-nervous and hormonal system
-blastocyst- typical in embryonic development
Describe plantae
-autotrophic- use photosynthesis
-growth restricted to meristems
-have cells surrounded by cellulose cell wall
-multicellular, eukaryotic
-contain chlorophyll
Describe fungi
-are eukaryotic
-have cell walls made of chitin
-saprotrophic- cause decay of organic matter
-can exist as single cells called yeast or they may have mycelium consists of hyphae
-unicellular or multicellular
Describe protoctista
-are eukaryotic
-mostly single celled (amoeba, paramecium) but can be multicellular e.g. algae
-mostly free living
-show wide variety of forms
-show various plant like or animal like features
-have autotrophic or heterotrophic nutrition- some photosynthesise, some ingest prey, some feed using extracellular enzymes and some are parasites
Describe prokaryote
-have no nucleus
-have loop of DNA that is not arranged in linear chromosomes
-have naked DNA not wound around histone proteins
-no membrane bound organelles
-have smaller ribosomes than in other groups
-have cells smaller than those of eukaryotes
-may be free living or parasitic
Why has evidence for classification evolved
-using observables features has created a largely successful classification of living things
-however since organisms adapt to their environment its possible 2 unrelated species could adapt similar ways and therefore look similar- convergent evolution
-these two species might be classified in same taxonomic group according to their observable features
-most recent research uses wider range of techniques and produced even more detailed evidence for classification
Biological molecules in classification
-evidence from biological molecules can help determine how closely related one species is to another
-certain larger biological molecules can help determine how they not identical in every species
-these are molecules involved in most fundamental characteristics of life, such as respiration and protein synthesis
-if we assume earliest living things had identical versions of these molecules then differences seen today as a result of evolution
-two organisms with similar molecules will be closely related as they have not evolved separately for long
-two organisms with very different versions of molecule are less closely related as they have evolved separately for longer
-differences between these molecules in different species reflect evolutionary relationships
-such evidence has largely backed up the evolutionary relationships that have already been worked out
-however, we can use it to clarify or correct relationships we are unsure about
BIOLOGICAL MOLECULES: cytochrome c
-a protein called cytochrome c is used in process of respiration
-all living organisms that respire must have cytochrome c but its not identical in all species
-also can be done for haemoglobin as universal and can be analysed for differences in amino acids
-proteins are large molecules made from chain of amino acids
-the amino acids in cytochrome c can be identified
-if we compare sequences of amino acids in samples of cytochrome c from two different species we can draw conclusions:
-if sequences are same, two species closely related
-if sequences are different, two species are not so closely related
-the more differences found between sequences less closely related the two species
BIOLOGICAL MOLECULES: DNA
-reflect evolutionary relationships
-another biological molecule found in all living organisms is DNA
-DNA provides genetic code- instructions producing proteins
-the code is same for all organisms- universal
-this means that particular sequence of DNA codes for same sequence of amino acids in bacterium as in any other organism
-changes to sequences of bases in DNA are called mutations
-mutations occur at random causing amino acid sequence change
-comparison of DNA sequences provides another way to classify species
-the more similar the sequence in a part of DNA the more closely related the two species
-if there are many differences, the species have evolved separately for a long time and they can be considered as less closely related
-this is probably most accurate way to demonstrate how closely related one species is to another
Describe three domain classification
-1990 Carl Woese suggested new classification system
-he based his ideas on detailed study of ribosomal RNA gene
-he divided kingdom Prokaryote into two groups: Eubacteria and Achaebacteria
-this division is based on fact bacteria are fundamentally different from Archaea and eukaryote
Structural differences of bacteria
-different cell membrane structure
-flagella with different internal structure
-different enzymes for synthesising RNA- RNA polymerase
-no proteins bound to their genetic material
-different mechanisms for DNA replication and synthesising RNA
Describe the features archaea share with eukaryotes
-similar enzymes for synthesising RNA e.g. RNA polymerase
-similar mechanisms for DNA replication and synthesising RNA
-production of some proteins that bind to their DNA
How did Woese devise the three domain system
-RNA and DNA are part of basic mechanism that translates genes into visible characteristics
-Woese argued that these differences between bacteria and archaea are fundamental
-he suggested that the two are more different from each other than the archaea and eukaryote
-therefore an accurate classification system must reflect this difference
-Woese three domain system of classification is now widely accepted by most biologists
Artificial classification
-some classification done for convenience
-for example in biology a wildflower guide often has all plants with yellow flowers on one page and all blue on another
-this is known as artificial classification
-based on only a few characteristics
-does not reflect any evolutionary relationships
-provides limited information
-is stable
Natural classification
-biological classification involves detailed study of individuals in a species
-individual members of a species will show variation
-for example all varieties of dog are of the same species
-underneath obvious visible differences all dogs very similar - we consider them to be closely related
-two closely related species will be placed in a group together- a genus
-closely related genera will be placed together in a larger group- a family
-these ranked groups create a hierarchy known as natural classification
-uses many characteristics
-reflects evolutionary relationships
-provides lots of useful information
-may change with advancing knowledge
-natural classification that reflects real relationships between groups could be very useful
-for example if we want to find out more about endangered species we may not want to risk harming any of few remaining members of species
-however if we know of another very similar species that is not endangered, we can carry out research on second species to provide applicable information to endangered species
What is phylogeny
-any two species living today have had common ancestor
-the time at which the two species started to evolve separately is a branch point on the tree
-the more recent the common ancestor the more closely related the two species are
-phylogeny is the study of evolutionary relationships between species
-it involves studying how closely different species are related
-it should be noted common ancestors do not survive today
-we cannot say that we evolved from apes, gorillas or modern day fish
-we evolved from ancestor that lived at some time in past
-it happens that the gorilla also evolved from the same ancestor
Define monophyletic group, phenetic concept, phylogenetic concept and species
MONOPHYLETIC GROUP -consists of ancestral species and all its descendants
SPECIES- group of individuals that actually or potentially interbreed - biological concept, however is issue of ring species
PHENETIC CONCEPT- set of organisms that are phenotypically similar
PHYLOGENETIC CONCEPT- may be determined by DNA
Who was Charles Darwin
-a naturalist who spent much of life observing and studying living organisms
-theory of evolution was not his idea
-the idea one species might evolve from another over time was not new but Darwin proposed mechanism for this process
-it cause certain amount upheaval in victorian britain as countered religious beliefs
-proposed natural selection- term used to explain how features of environment apple selective force of reproduction of individuals in a population
Research of Charles Darwin
-Darwins ideas began developing during 5yr trip around world in ship called HMS beagle
-visited galapagos islands where discovered unusual species
-many species similar to those on south american mainland
-there was clear variation between members of same species found on different islands
-also noted what appeared to be wide variety of bird species were actually closely related finches
-Darwin concluded that one species had arrived on islands from mainland and then evolved to form different species
Who was Alfred Wallace
-another naturalist who independently came to same conclusion as Darwin
-Wallace had made collections in both Amazon and south east Asia
-their first publications were joint papers on subject of evolution by natural selection
-soon followed by Darwins book the origin of species
What observations did Darwin make
1) offspring generally appear similar to parents
2) no two individuals are identical
3) organisms have ability to produce large numbers of offspring
4) populations in nature tend to remain fairly stable in size
How are Darwins conclusions summarised
-there is struggle to survive
-better adapted individuals survive and pass on their characteristics
-over time number of changes may give rise to new species
EVOLUTION EVIDENCE: fossil evidence
-in past world was inhabited by species that were different from those present today
-old species have died out and new species have arised
-new species that have appeared are often similar to older ones found in same place
-Darwin began to understand that fossil species gave rise to more modern species and he felt this must be because more modern species had variations that were better adapted to environment
-also found that many fossil species were much larger than modern but otherwise appeared very similar
-for example some modern species of armadillo grow to only 15cm long whilst glyptodont was many times this size
-one most complete fossil records for evolution is hors
-the similarity of fossil sequences of horse provide evidence that one species arose from a previous one
EVOLUTION EVIDENCE: biological molecules
-recent study of biological molecule provides very strong evidence for evolution
-the fact certain molecules are found throughout living world is evidence in itself
-if one species give rise to another, both are likely to have same biological molecules
-this suggests the all species arose from one original ancestor
-two closely related species will have separated only relatively recently- their biological molecules are likely to be identical or very similar
-in species that took separate evolutionary paths a long time ago their biological molecules are likely to differ more
-evidence from molecules such as cytochrome c and other proteins show this pattern of changes
-genes can be compared by sequencing bases in DNA
-the greater number of similarities between gene sequences the more closely related species and more recent their evolution
-also shows that more distantly related species the more differences in the DNA
Steps to natural selection
1)overproduction
2) competition
3) variation, better adapted
4) due to genetic variation in alleles, through mutation/ meiosis
5) selection pressures in environment determine which will survive
6) live longer- survival of fittest
7) other die younger
8) reproduce more; more offspring
9) alleles passed to offspring
10) offspring have more appropriate characteristics
11) many generations
12) beneficial alleles increase in frequency= evolution
Define speciation
formation of new species from an existing one
Differences between individuals
-presence of difference between individuals is called variation
-no two individuals are exactly alike, however similar may look
-identical twins start as one cell that divides and separates into two
-each two cells develops into a separate person
-whilst 2 original cells had same genetic information, subsequent replication of DNA and cell divisions may have introduced changes to DNA
-also slight environmental differences in womb or after birth can mean that the individuals show physical differences
Variation within species
-like any other species, humans show variation
-if you think of almost any characteristic there will differences between members of population- for example eye colour, hair colour, nose shape
-these differences known as intraspecific variation
-greater the genetic diversity of species, greater intraspecific variation
Variation between species
-variation that occurs between species usually obvious
-this variation usually used to separate members of one species from another
-variation between species is called interspecific variation
Continuous variation
-continuous variation is where there are two extremes and a full range of intermediate values between them
-most individuals close to mean value
-number of individuals at extremes is low
-continuous variation is often regulated more than one genes and can be influenced by the environment in which an organism lives
-examples of continuous variation include: height in humans, length of leaves, number of flagella on bacterium
-this type of variation usually quantifiable and best to plot data using histogram
Discontinuous variation
-discontinuous variation is where there are two or more distinct/ discrete categories with no intermediate values
-the members of a species may be evenly distributed between the different forms or there may be more of one type than the other
-discontinuous data usually regulated by a single gene and is not influenced by environment in which organism lives
-examples of discontinuous variation includes: gender, human blood groups
-discontinuous data can be shown on bar chart
VARIATION CAUSES: inherited or genetic variation
-the genes we inherit from our parents provide information that is used to define all our characteristics
-the combination of alleles that we inherit is not the same as that in any other living thing
-we may share many alleles with other members of out species and we share genes with members of other species
-however there is never a complete match
-human cells contain approximately 20,000 genes
-many of these have more than one allele
-the chances of any two individuals having exactly same combination of alleles is remote
-so the combination of characteristics that each of us possess is unique
VARIATION CAUSES: environmental variation
-many characteristics can be affected by environment
-for example an overfed pet will be obese
-a persons skin will become tan/darker with careful exposure to sun
-a hawthorn tree usually grows upright to height on 6m but if nibbled by animals/ cut by farmer it will become bushy
-in this case, environment affected the way it grows
-if hawthorn grows in rock crevice with very little soil or water it may grow to only 150cm
VARIATION CAUSES: combined effects
-environmental variation and genetic variation are not isolated
-in past century humans have become taller as result of better diet
-however good diet may be you are unlikely to grow very tall if rest of family is short- this is because height you can reach is limited by genes
-not all our genes are active at any one time
-for example when we reach puberty many changes occur in our body because different genes become active
-changes in the environment can also directly affect which genes are active
