4.3 Classification and Evolution Flashcards
what is variation
the difference in characteristics that exist between individuals/organisms
what are the 2 types of variation
intraspecific and interspecific
what is intraspecific variation, and include examples
- variation within a species
- individual European robins weighing different weights, and having variation in length, wingspan, colour, beak size
what is interspecific variation, and give examples
- variation between different species
- lightest species of bird weigh a lot less than the heaviest species
what are the two factors that cause variation
genetic and environmental (can be both)
explain genetic factors
1) ALLELES: different species have different genes, but individuals of the same species have same genes, but different versions (alleles). you inherit your genes from your parents, so genetic factors are inherited
2) MUTATIONS: change in DNA base sequence changes the protein coded for, affecting physical and metabolic characteristics (in body cells or gametes, which will be passed on)
3) MEIOSIS: crossing over and independent assortment of chromosomes
4) SEXUAL REPRODUCTION: inherit alleles from each parent, so individual to the parents
5) CHANCE: which gametes combine during sexual reproduction
examples of genetic factors affecting variation
- blood groups (made of alleles A, O and B, producing groups depending on combination from parents (A, O, and AB)
environmental factors causing variation
- caused by differences in environment
- climate, food, lifestyle
- these factors can change in an organism’s life
- affect plants greater, as they cannot move
examples of factors caused by only environmental factors
accents, pierced ears, scars
factors affecting variation which have both genetic and environmental causes
- genetic determine the characteristics your born with, but environmental can influence how they develop
examples of variation caused by both the environment and genetics
- HEIGHT: genes determine how tall an organism can grow, but diet and nutrient availability affects how tall a person will actually grow
- FLAGELLUM: genes determine if a microorganism can grow a flagellum, but some will only start to grow in certain environments (e.g. if metal ions are present)
- SKIN COLOUR: born with one, but may get darker if more exposure to UV radiation from the sun
what is continuous variation
individuals in a population vary within a range, no distinct categories
- normally controlled by a number of genes
- can be plotted in a frequency table, then plotted on a histogram, with curve drawn to show the trend
examples of continuous variation
ANIMALS: milk yield, mass
PLANTS: number of leaves, mass (of seeds)
MICROORGANISMS: width, length(of flagellum)
what is discontinuous variation
there are two or more distinct categories that an individual can fall in, only one of them and no intermediates
- can be grouped
- shows via a bar chart
what are examples of discontinuous variation
ANIMALS: blood group
PLANTS: colour, seed shape
MICROORGANISMS: antibiotic resistance, pigment production
what do you usually get when plotting continuous variation data (via samples from population) on a graph
normal distribution curve (bell-shaped)
- can show variation between samples
what is mean, mode and median
mean= average of values collected in a sample
mode= most common value
median= middle value when ordered
- all the same in normal distribution curve
what are characteristics of a normal distribution curve
- symmetrical about the mean
- 50% of values are below and 50% are above the mean
- most values lie close to mean, with very few on the extreme sides
what is standard deviation
measure of the spread of values about the mean
- tells you how much the values in a single sample vary
what does 9±3 mean
- the mean is 9
- the standard deviation is 3
- most of the values are spread between 6 and 12
what does a large standard deviation mean
the values in the sample vary a lot
- the graph will be fatter
what does a small standard deviation mean
most of the sample data is around the mean value, so varies little
- graph will be steep
how do you calculate standard deviation
1) calculate the mean
2) subtract the mean from each value
3) square each answer
4) add all answers
5) divide by number of values - 1
6) square root your answer
what do data sets being correlated mean
if two sets of data are related
what are the 3 types of correlation
- POSITIVE (as one set of data increases in value, the other set of data also increases in value (or both decrease) [+1]
- NEGATIVE (as one set of data increases in value, the other set of data decreases in value) [-1]
- NONE (no relationship between the data) [0]
what is the Spearman’s rank correlation coefficient used to show
the strength of correlation of 2 sets of data
how do you calculate Spearman’s rank correlation coefficient
what is students t- test
how do you calculate a t-test
what are adaptations
characteristics that increase an organism’s chance of survival and reproduction in its environment, as well as it’s offspring’s chances of reproducing successfully
what are the 3 types of adaptations
anatomical, behavioural, physiological
why do adaptations develop
due to evolution by natural selection:
- in each generation, the best-adapted individuals are more likely to survive and reproduce, passing their adaptations onto their offspring
- individuals that are less well adapted are more likely to die before reproducing
what are behavioural adaptations
the way in which an organisms ACTS to increase its chance of survival
- fall into 2 categories:
- innate/intrinsic, which they’ve inherited through genes (spider web)
- learned behaviour, from observing other animals
examples of behavioural adaptations
- possums sometimes “play dead” if being threatened by a predator to escape the attack (increasing their chance of survival) - - scorpions dance before mating, to make sure they attract a mate of the same species, increasing the likelihood of successful mating
- seasonal behaviours, like migration for more favourable conditions
what are physiological adaptations
processes inside an organism’s body that increase its chance of survival
examples of physiological adaptations
- brown bears hibernating, which lowers their rate of metabolism (all the chemical reactions taking place in the body) over winter, so that they can conserve their energy and don’t need to look for food in the months when it’s scarce (increasing their chances of survival)
- some bacteria produce antibiotics, to kill other species of bacteria in the area, so there is less competitions (more likely to survive)
- poison production, to kill prey or protect from predators
- water holding, to survive in times of scarce water
what are anatomical adaptations
structural features of an organism’s body that increase its chance of survival
examples of anatomical adaptations
- otters have streamlined shape, making it easier to glide through the water, so easier to catch prey and escape predators (increasing their chances of survival)
- whales have a thick layer of blubber, helping them to keep warm in the cold sea, increasing their chances of survival in places where their food is found
why do some organisms from different taxonomic groups have similar features
- even though they aren’t closely related
- the organisms have evolved in similar environments, and to fill similar ecological niches (the role of an organism within its environment)
what is convergent evolution
when two species evolve similar characteristics independently of each other, because they have adapted to live in similar environments
what are analogous structures
structures that have adapted to perform the same function but have a different genetic origin
what is the key example when observing convergent evolution
marsupial and placental moles
what are the 3 different types of mammals, and what are the 2 key groups you need to know about
1) placental mammals (most)
2) marsupial mammals
3) very few are egg-laying monotremes
where are marsupial mammals mostly found
- in Australia and the Americas
- diverged from placental mammals many millions of years ago
- have been evolving away from placental mammals since
characteristics of marsupial mammals
- have a short gestation period (pregnancy)
- don’t develop a full placenta
- are born early into their development, and climb into their mother’s pouch, where they become attached to a teat and receive milk whilst they continue to develop
- e.g. kangaroos
characteristics of placental mammals
- a longer gestation period
- develop a placenta during pregnancy, which allows the exchange of nutrients and waste products between the fetus and mother
- are born more fully developed
- e.g. humans
why are the 2 types of moles not closely related
- they evolved independently on different continents
- they do share similar anatomical features though (they look alike) as they’ve both evolved in similar environments
how do both types of moles live similarly
- both live in tunnels in the ground
- both burrow to reach their food supply (earthworms, insects and other invertebrates)
how are both types of moles similarly adapted
- small or nonexistent eyes because they don’t need to be able to see underground
- no external ears, to keep a streamlined head for burrowing
- scoop-shaped and powerful front paws, which are good for digging
- claws that are specialised for digging
- tube shaped body and cone shaped head, making it easier to push through sand and soil
what is evolution
the slow and continual change of organisms from one generation to the next
when and what did Darwin publish about evolution
Theory of Evolution by Natural Selection
- 1859
what were Darwin’s 4 observations about the world around him
- organisms produce more offspring than survive
- there’s variation in characteristics of members of the same species
- some of these characteristics can be passed on from one generation to the next
- individuals that are best adapted to their environment are more likely to survive
what is natural selection
one process by which natural selection can occur
explain evolution by natural selection
1) individuals within a population show variation in their characteristics (phenotype)
2) may be due to different alleles being present, as a result of mutation
3) selection pressures (environmental factors such as predators, disease and competition) create a struggle for survival
4) individuals with best adapted characteristics for selection pressures are more likely to survive and breed, reproducing successfully
5) opposite is also true, and those less well adapted are less likely to survive and reproduce
6) those who survive will pass on their alleles for the advantageous characteristics to their offspring, and the process repeats over generations
7) over time, the proportion of the population receiving the advantageous alleles and characteristics increases
8) over generations, this leads to evolution as favourable characteristics become more common in a population
what are selection pressures
factors that affect the organism’s chances of survival and reproductive success
overview the evolution of peppered moths
- originally, moths were a pale colour, providing camouflage against the light coloured tree bark, increases chances of survival
- after the industrial revolution, tree bark became darker, partly due to the soot from factories
- dark moths were now better adapted to camouflage, so more likely to survive, reproduce and pass the allele for dark colour onto offspring
- after the clean air act, levels of pollution from factories decreased, the bark became lighter, so frequency of the pale allele in the gene pool once again increased
explain the relationship between genes, alleles and phenotypes
- genes determine many of an organisms characteristics
- individuals show variations in their phenotypes partly due to genetic variation, e.g. the different alleles they have
- when an organism with advantageous alleles reproduces
- the alleles that determine those characteristics can be passed onto the offspring
who was Alfred Russel Wallace
- a scientist that worked at the same time as Darwin
- played an important role in developing the theory of evolution by natural selection
what did Wallace discover
- independently came up with the idea of natural selection and wrote to Darwin about it
- Darwin and Wallace published their papers about evolution together and acknowledged each others work (didn’t always agree on the same mechanisms involved)
- Wallace’s observations provided lots of evidence to support the theory
- e.g. warning colours are used by some species to deter predators from eating them, and this is an example of an advantageous adaptation evolved via natural selection
why is Wallace less recognised for theory of evolution via natural selection than Darwin
- it wasn’t until Darwin published “On the Origin of Species” that scientists really paid attention to the theory
- this book is why Darwin is better remembered than Wallace, even though he helped come up with the theory
what did Darwin discuss in his book “On the Origin of Species”
- gave lots of evidence to support the theory
- expanded on the theory
- wrote about all the species he had observed during his voyage in South America and Galapagos Islands in 1830s
what are the 3 types of evidence used to support evolution
- fossil records
- DNA evidence
- molecular evidence
what fossil record evidence is there to support the theory of evolution
- fossils are remains of organisms preserved in rocks
- we can arrange fossils in chronological order to see the gradual changes in organisms as evidence of evolution
- e.g. fossil records of horses show their gradual change in increasing size and hoof development
what DNA evidence is there to support the theory of evolution
- evolution suggests that all organisms evolved from shared common ancestor
- closely related species diverged more recently
- evolution is caused by gradual changes in the base sequence of an organisms DNA
- organisms that diverged more recently have more similar DNA, as less time has passed for changes in their DNA sequence to occur
-e.g. humans, mice and chimps all evolved from a common ancestor, but humans and mice diverged a long time ago whereas humans and chimps diverged more recently - the DNA sequence of humans and chimps is 94% the same, but with mice is only 85% the same
what is the additional DNA evidence of evolution found in eukaryotes
- in eukaryotes, most DNA is found in the nucleus
- BUT also have DNA in mitochondria
- scientists can also observe differences in mitochondrial DNA to learn about evolutionary relationships between species, and see how closely related the organisms are
what are pesticides
chemicals that kill pests, insects that damage crops
what have some insects been able to do via evolution
- evolve pesticide resistance
- e.g. some populations of mosquito have evolved resistance to pesticide DDT
- e.g. some populations of pollen beetles (damage the crop oilseed rape) are resistant to pyrethroid pesticide
how have some insects developed pesticide resistance
VIA NATURAL SELECTION:
- there is variation in a population of insects
- genetic mutations create alleles that make some insects resistant to a pesticide
- if the population is exposed to that pesticide, only the individuals with resistance will survive and reproduce
- the alleles for pesticide resistance will be passed on to the next generation
- causes the population to evolve
- and more individuals will carry the allele than the previous population (becomes widespread)
- the pesticide acts as a SELECTION PRESSURE, and without it, natural selection will not take place
what are the implications for humans of pesticide resistance
- crop infestations with pesticide resistant insects are harder to control
- some insects are resistant to lots of different pesticides
- can take farmers a while to figure out which pesticide will actually kill the insects, and in that time, all crops could be destroyed
- if insects are resistant to specific pesticides, farmers might have to use broader pesticides, which could kill beneficial insects
- disease-carrying insects could become pesticide-resistant, increasing the spread of disease
- a population of insects could evolve to become resistant to all pesticides, so new pesticides need to be produced, taking time and costing money
how has drug resistance occurred
- via evolution on antibiotic resistant bacteria, e.g. MRSA
- other pathogens can also develop resistance to specific drugs
- e.g. some protoctists that cause malaria are resistant to several drugs used to treat it
what are the implications of drug resistance on humans
- infections caused by drug-resistant microorganisms are harder to treat, especially if the the microorganism is resistant to lots of different drugs
- can take doctors a while to figure out which drugs will get rid of infection
- in this time, patients can become very ill and die
- a pathogen could become resistant to all drugs
- so new drugs need to be developed, costing money and taking time
what is classification
the act of arranging organisms into groups based on their similarities and differences
- makes it easier for scientists to identify and study them
what is taxonomy
the study of classification
how is the classification system structured
the organisms are placed into groups in a taxonomic hierarchy
what are the groups called in the taxonomic hierarchy and how many are there
- taxonomic groups
- 8 levels
explain how organisms are sorted in the taxonomic hierarchy
- all with similar organisms being grouped together at each stage
- as you move down, there are fewer organisms in each group
- species only has one type of organisms
what are the 8 levels of taxonomic hierarchy
Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species
how many kingdoms are there
5
what are the 5 kingdoms
- prokaryotae
- protoctista
- fungi
- plantae
- animalia
characteristics of prokaryotae
- prokaryotic
- unicellular
- no nucleus
- less than 5 micrometers
e.g. bacteria
characteristics of protoctista
- eukaryotic cells
- usually live in water
- single- celled
- or simple multicellular organisms
e.g. algae, or protozoa
characteristics of fungi
- eukaryotic
- chitin cell wall
- saprotrophic (absorb substances from dead or decaying organisms)
- single-celled or multicellular organisms
e.g. moulds, yeasts, mushrooms
characteristics of plantae
- eukaryotic
- multicellular
- cell walls made of cellulose
- can photosynthesise
- contain chlorophyll
- autotrophic (produce their own food)
- phototrophic (… using light)
characteristics of animalia
- eukaryotic
- multicellular
- no cell walls
- heterotrophic (consume plants and animals)
what system is used to name animals
binomial naming system (nomenclature)
explain binomial nomenclature
- all organisms are given one internationally accepted name in latin
- has two parts:
1) first part is genus, CAPITAL
2) second part is species, in lower case - always written in italics, or underlined if hand written
- helps to avoid confusion, and see close relationship between species with same genus
what is phylogeny
- the study of the evolutionary history of groups of organisms
- tells us who’s related to whom, and how closely related - shows evolutionary RELATIONSHIPS
what do phylogenetic trees show
- common ancestors between organisms
- closely related species diverged away from each other more recently
what is phylogenetic tree concept
species is the smallest group that share a common ancestor, so the end of a branch on a tree
does classification take into account phylogeny
yes, when arranging into groups, called cladistics
why may phylogeny be used over normal classification
- produce continuous trees, so organisms not forced into specific groups
- shows evolutionary relationships
how were animals originally classified
- only using observable features to place them into groups
- problematic as scientists don’t always agree on the relative importance of different features
- doesn’t show how related they all are, like sharks and whales
if organisms are closely related, what can be said about how related they are
the more closely they are related
how do we now figure out how closely related
- observable features along with other evidence, to see how similar, and therefore related organisms are
how is molecular evidence used in classification
- the similarities in proteins and DNA
- the more closely related, the more similar the molecules
- compare how DNA is stored and the sequences of DNA bases
- compare the sequence of amino acids in a protein from different organisms
- e.g. cytochrome C comparisons (as a short protein found in many organisms) and how closely related the amino acid sequences are in two different species
how are the other evidences used in classification
- embryological, for similarities in early stages of an organism’s development
- anatomical, for structure and function of different body parts
- behavioural, for similarities in behaviour and social organisation
what are examples of new technologies that have been able to assist in classification
new DNA techniques and better microscopes
how have new technologies been able to assist in new discoveries of classification
- new technologies mean new discoveries can be made
- relationships between organisms can be clarified
- scientists can also share their new discoveries in meetings and scientific journals
- the classification of animals is continually being revised to take account of any new findings scientists discover
give an example of where the classification of an animal was revised upon new discoveries
- skunks were classified into family Mustelidae
- until molecular evidence revealed their DNA sequence was significantly different from other members of the family
- reclassified into new family Mephitidae
what has the 5 kingdom classification system now been replaced with
three domain system (1990)
what are the differences between the older 5 kingdom system and the newer three domain system
- in older system, the largest groups were the 5 kingdoms, and all organisms were placed into one of these groups
- in the new system, there are 3 domains, which are the larger superkingdoms above the kingdoms in the taxonomic hierarchy
- in 3 domain system, organisms in prokaryotae (unicellular organisms without a nucleus) are separated into two domains, Archaea and Bacteria
- organisms with cells containing nucleus are placed in domain Eukarya (4/5 kingdoms)
- the lower hierarchy stays the same
why was the three domain system proposed
due to new evidence, mainly molecular
- e.g. Prokaryotae were reclassified into two domains because new evidence showed a large difference between them
what is the evidence present to suggest that Archaea and Bacteria should be 2 different domains
MOLECULAR: enzyme RNA polymerase is different in Bacteria to Archaea (Archaea have similar histones (proteins that bind to DNA) to Eukarya)
CELL MEMBRANE: bonds of the lipids in cell membranes of Bacteria and Archaea are different, as well as the development and composition of flagellae
what is the modern scientific consensus of how organisms are classified
- most scientists agree that Archaea and Bacteria evolved separately
- believe that Archaea are more closely related to Eukarya than Bacteria
- EXAMPLE OF HOW SCIENTIFIC KNOWLEDGE IS ALWAYS CHANGING AND IMPROVING
