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classification and evolution (variation (variation can be continuous…
classification and evolution
classification basics
classification involves grouping similar organisms together
taxonomy= the study of classification
classification= the act of arranging organisms into groups based on their similarities and differences
taxonomic hierarchy= Domain, Kingdom, Phylum, Class, Order, Family, Genus, Species
organisms can be placed into 1 of 5 kingdoms
prokaryotae= prokaryotic, unicellular, no nucleus, less than 5 ym e.g. bacteria
protocista= eukaryotic cells, usually live in water, single celled or simple multicellular organisms e.g. algae
fungi= eukaryotic, chitin cell walls, saprotrophic (absorb substances from dead and decaying organisms), single or multicellular organisms e.g. mould, yeast
plantae= eukaryotic, multicellular, cellulose cell walls, can photosynthesise, contain chlorophyll, autotrophic (produce own food) e.g. mosses, ferns
animalia= eukaryotic, multicellular, no cell walls, heterotrophic (consume plants and animals)
binomial naming system
genus has a capital letter
species is lower case
UNDERLINE BINOMIAL NAME
avoids confusion of using common names which can be used to refer to lots of the different species
phylogeny gives evolutionary history of organisms
tells how closely related different species are
all organisms have evolved from a common ancestor
each branch represents a new common ancestor in a phylogenetic tree
artificial classification= is based only on a few characteristics, doesn't reflect any evolutionary relationships, provides limited info, is stable
natural classification= uses many characteristics, reflects evolutionary relationships, provides lots of info, may change with advancing knowledge
evolution of classification systems
classification systems are now based on a range of evidence
observable features aren't always enough
observable features were used to place organisms into groups e.g. number of legs
scientists don't always agree on the relative importance of different features and groups based solely on physical features may not show how related organisms are
other evidence
molecular evidence= the similarities in proteins and dna, more closely related organisms will have more similar dna molecules, you can compare how dna is stored and the sequence of dna bases, you can compare the sequence of amino acids in proteins e.g. cytochrome c (more similar the amino acid sequence of cytochrome c, the closer related the species are)
embryological evidence= the similarities in the early stages of an organisms development
anatomical evidence= the similarities in structure and function of different body parts
behavioural evidence= the similarities in behaviour and social organization of organisms
new technology
new tech can result in new discoveries being made and the relationships between organisms being clarified
scientists can share their discoveries in scientific journals, how organisms are classified is continually revised
five kingdoms vs three domains
in the three domain system the organisms that were prokaryotae are separated into the 2 domains Archaea and Bacteria
organisms that contain a nucleus are placed into eukarya
supported by molecular evidence
the enzyme rna polymerase is different in bacteria and archaea, archaea have similar histones to eukarya
the bonds of lipids in cell membranes of bacteria and archaea are different, the development and composition of flagella are also different
variation
variation exists between all individuals
intraspecific= variation within a species
interspecific= the variation between different species
variation can be continuous
continuous variation= when the individuals within a population vary within a range
e.g. humans can weigh any mass within a range
e.g. number of leaves on a plant can vary within a range
e.g. width of bacteria can vary within a range
discontinuous variation
discontinuous variation= when there are 2 or more distinct categories - each individual falls into one of these categories and there are no intermediates
e.g. blood group, seed shape of plants, antibiotic resistance, pigment production
variation can be caused by genes, environment or both
genetic factors
different species have different genes
individuals of the same species have the same genes but different alleles (versions)
the genes and alleles of an organism makes up its genotype
the differences in genotype result in variation in phenotype (characteristics displayed by organism)
genetic factors are inherited (from parents)
environmental factors
variation can be caused by differences in the environment
characteristics controlled by environmental factors can change over an organisms life
e.g. accents, ears pierced
both
genetic factors determine the characteristics an organisms born with, but environmental factors can influence how some develop
height- genes determine how tall and organism could grow, but diet or nutrient availability affect how tall an organism actually grows
flagellum- genes determine if a microorganism can grow a flagellum but some will only start to grow them in certain environments
you can use mean to look at variation samples
most samples will have a bell shaped graph
standard deviation
standard deviation= how much the values in a single sample vary
a large standard deviation means the values in the sample vary a lot
adaptations
adaptations make organisms well suited to their environment
being adapted to an environment means an organism has features that increase its chance of survival and reproduction and also the chances of its offspring reproducing successfully
in each generation, the best adapted individuals are more likely to survive and reproduce, passing their adaptations to their offspring
adaptations develop because of evolution by natural selection
adaptations can be behavioural, physiological and anatomical
behavioural adaptations
e.g. possums play dead if their threated by a predator increasing their chance of survival
e.g. scorpions dance before mating to make sure they attract a mate of the same species, increasing the likelihood of successful mating
physiological adaptations
processes inside the body that increase the chance of survival
e.g. some bacteria produce antibiotics which kill other bacteria and reduce competition, increasing chance of survival
anatomical adaptations
structural features of an organisms body that increase its chance of survival
e.g. whales have a thick layer of blubber which keeps them warm increasing their chance of survival
organisms from different taxonomic groups may have similar features even though there not closely related e.g. have evolved in similar environments to fill similar ecological niches
marsupial and placental mammals have evolved separately
marsupial mammals
short gestation (pregnancy) period
don't develop a full placenta
are born early in development and climb into mothers pouch where they receive milk and continue to develop
placental mammals
have a longer gestation period
develop a placenta during pregnancy which allows the exchange of nutrients and waste products between fetus and mother
are born fully developed
marsupial and placental moles look alike but aren't closely related
they evolved separately on different continents
they share similar anatomical features because they both evolved to live in similar environments
both have: small/ non existent eyes, no external ears, scoop shaped and powerful front paws for digging, claws for digging, a tube shaped body and cone shaped head which make pushing through soil/sand easier
the theory of evolution
Darwin published his theory of evolution by natural selection in 1859
observations
organisms produce more offspring than survive
theres variation in the characteristics of members of the same species
some of these characteristics can be passed from one generation to the next
indivduals that are best adapted to their environment are more likely to survive
theory
1) individuals in a population show variation in their phenotypes
2) selection pressures create a struggle for survival
3) individuals with better adaptations are more likely to survive and have reproductive success, passing on their adaptation to offspring
4) over time the proportion of the population with the advantageous adaptation increases
5) over time this leads to evolution as favourable adaptations become more common in a species
MARO
Wallace
independently came up with theory of natural selection
Wallace's observations of warning colours used by some species of butterfly to deter predators is an example of an advantageous adaptation
evidence
fossil record
fossils= remains of organisms preserved in rocks
by arranging fossils according to date gradual changes in organisms can be observed
dna evidence
evolution is caused by gradual changes in the base sequence of an organisms dna
organisms that have recently diverged have more similar dna
look at mitochondrial dna and nuclear dna
molecular evidence
scientists compare the sequence of amino acids in proteins and antibodies
organisms that have diverged more recently have more similar molecules
populations of insects can evolve resistance to insecticides due to natural selection
implications of pesticide resistance
crop infestations are harder to control, the use of broader pesticides could harm beneficial insects
spread of diseases
if a population becomes resistant to all, lots time and money would have to be invested to create a new one
implications of drug resistance
MRSA (mutate, resist, survive, alone)
infections would be harder to treat
expensive to create new drugs
