1
Q
Why do we classify living things
A
For our convenience, to make the study of living things more manageable, to make it easier to identify organisms, to help us see the relationship between species
2
Q
Who first classified living things, how did they do this, what did they produce
A
- Carl Linnaeus- 1735
- catergorized according to visible features
- 5 main groups- Kingdoms- Plantae, Animalia, Fungi, Protoctista, Prokaryote
- after Kingdom there is phylum, class, order, family, genus and species
3
Q
Who added to Carl Linnaeus’ classification system, how
A
- Carl Woese - 1977
- added domain (highest taxonomic rank) - 3- Archaea, Eubacteria and Eukaryote
4
Q
Describe the current system of classification
A
8 Taxonomic ranks:
- domain- the highest taxonomic rank- 3- Archaea, eubacteria, eukaryotae
- Kingdom- Traditionally 5 main- prokaryotae (eubacteria, archaea), protoctista, fungi, plantae, animalia
- phylum- a major subdivision of the Kingdom- contains all the groups of organisms that have the same body plan (e.g. possession of a backbone)- 2 in the animal kingdom- Chortata (CNS along back), Arthropoda (exoskeleton)
- class- a group of organisms that all possess the same general traits (e.g. same number of legs)
- order- a subdivision of the class using additional information about the organisms, such as meat eating and vegetation eating animals
- family- a group of closely related genera, such as the dog and cat family
- genus- a group of closely related species
- species- the basic units of classification. All members of a species show some variations, but all are essentially the same.
mnemonic- kings (and) princes can often find grass snakes
5
Q
Describe the binomial naming system
A
- genus name followed by species name
- genus name always capitalised, species name not capitalised
- typed or printed text- italics
- handwritten- underlines
- e.g.- humans = Homo sapiens
- Latin- universal language- whenever a species is named, it is given a universal name- every scientist in every country will use the same name- avoids the potential confusion caused by using common names
6
Q
Who developed the binomial naming system, why
A
- Carl Linnaeus
- before, species were identified by a common name, or a long and detailed description
- using a common name doesn’t work well because the same Organism may have a completely different common name in different parts of one country, different common names are used in different countries, translation of languages or dialects may give different names, the same common name may be used for different species in other parts of the world
7
Q
When classifying an Organism, why is it important to study each specimen in detail
A
- at the higher levels of the ranked system the differences between the organisms can be very great- quite easy to place a species into its domain, Kingdom or phylum
- class can be a little more difficult as the differences between the classes in one phylum may not be very great- longer description of the species may be needed
- as you descend to the lower taxonomic groups, it becomes increasingly difficult to separate closely related species and to place a species accurately- a more and more detailed description of the species is needed
8
Q
What are two definitions of a species, why do we need the second
A
- biological definition- a group of organisms that can freely interbreed to produce fertile offspring
- this definition does not work for organisms that reproduce asexually, and it is very hard to apply to organisms that are known only as fossils
- phylogenetic definition- a group of individual organisms that are very similar in appearance, anatomy, Physiology, biochemistry and genetics
9
Q
Describe the development of classification
A
- being so similar, the members of a species occupy the same niche in an ecosystem- this fact was used in early classification systems which were based only on appearance and anatomy
- however, it is easy to make mistakes- for example Aristotle classifieds all living things as either plant or animal, and further subdivided the animals into those that live and move in water, live and move on lands, move through the air- based on similarities he observed- but this groups fish with turtles, birds with insects, mammals with frogs
- such early classifications have been adapted and made more accurate as more research is carried out and more information becomes available
- the early classification systems of Linnaeus and other scientists were based on observable features- means they were limited to those features of organisms that you can see
- by the 17th century, scientists had microscopes to help
- traditionally, all living things have been grouped into a number of kingdoms- for many years, the generally accepted number was two- plants or animals- as more living things were discovered and studied closely, it became clear that not all could fit easily into one of these categories
- in the early 2 Kingdom classification systems, the animal Kingdom includes single celled organisms that had some animal like features, and the plant Kingdom included single celled organisms that had plants like features
- later, electron microscopes revealed further details inside cells- made it clear that many single celled organisms share some of the features of both plants and animals- such as chloroplast’s as well as using a flagellum to move around- doesn’t fit clearly into plant or animal
- fungi didn’t fit in either- don’t move about like animals, and the hyphae grow into the surrounding substrate in the same way as roots do, however they do not photosynthesise and they digest organic matter and absorb the nutrients like animals
- Led to adoption of 5/6 kingdom classification system- still based on the observable features of their anatomy, but at a microscopic level
10
Q
What are the domains and kingdoms included within them
A
3 domains, 6 kingdoms
Archaea- Archaebacteria
Bacteria- Eubacteria
Eukaryota- Plantae, Fungi, Protoctista, Animalia
11
Q
Diagnostic features of archaea
A
- have no nucleus
- have a loop of DNA that is not arranged in linear chromosomes
- have naked DNA- DNA that is not associated with histone proteins
- have no membrane bound organelles
- have smaller ribosome’s than in in other groups
- have cells smaller than those of eukaryotes
- may be free living or parasitic (some cause disease)
- e.g. crenarchaeota
12
Q
Diagnostic features of Eubacteria
A
- have no nucleus
- have a loop of DNA that is not arranged in linear chromosomes
- have naked DNA- DNA that is not associated with histone proteins
- have no membrane bound organelles
- have smaller ribosome’s than in in other groups
- have cells smaller than those of eukaryotes
- may be free living or parasitic (some cause disease)
- e.g. E coli bacteria
13
Q
Diagnostic features of Protoctista
A
- are eukaryotic
- are mostly single celled, but many algae are multi cellular
- show a wide variety of forms- the only thing that all protoctists have in common is that they do not qualify to belong to any of the other four kingdoms
- show various plant like or animal like features
- are mostly free living
- autotrophic or heterotrophic nutrition- some photosynthesise, some ingest prey, some feed using extracellular enzymes (like fungi do), and some are parasites
- e.g. paramecium
14
Q
Diagnostic features of Fungi
A
- eukaryotic
- time exist as single cells called yeasts, or they have a mycelium that consists of hyphae
- have walls made of chitin
- have cytoplasm that is multinucleate
- are mostly free living and saprophytic- meaning that they can cause decay of organic matter
15
Q
Diagnostic features of plantae
A
- are eukaryotic
- are multicellular
- are autotrophic- absorb simple molecules and build them into larger organic molecules
- contain chlorophyll
16
Q
Diagnostic features of animalia
A
- are eukaryotic
- are multicellular
- heterotrophic- digest large organic molecules to form smaller molecules for absorption
- are usually able to move around
17
Q
Describe artificial classification
A
- classification done for convenience
- group things in a way that is easy to remember or in a way that makes it easy to find a particular item
- is based on only a few characteristics
- doesn’t reflect any evolutionary relationships
- provides limited information
- is stable
18
Q
Describe natural classification
A
- biological classification involves detailed study of the individuals in a species- they will show variation- as all members of species such as dogs are very similar, we can consider them to be closely related
- different species that are very similar can be considered to be closely related- a genus
- closely related genera will be placed together in a family
- in this way, the whole of the living world can be organised into a series of ranked groups- a hierarchy
- uses many characteristics
- reflects evolutionary relationships
- provides a lot of useful information
- may change with advancing knowledge
19
Q
How may a natural classification be useful
A
- a natural classification that reflects real relationships between the groups could be very useful- for example, if we want to find out more about a rare or endangered species, we may not want to risk harming any of the few surviving members of that species. However, if we know of another very similar species that is not endangered, we can carry out research on this second species to provide information that is also applicable to the endangered species- may help us to make conservation more successful.
20
Q
What is Phylogeny, describe the process
A
- the study of the evolutionary relationships between species
- it involves studying how closely different species are related
- we can think of all organisms as belonging to an evolutionary tree
- any two species living today have had a common ancestor at some time in the past
- the time at which the two species started to evolve separately is a branch point on the tree
- the common ancestor appears on the tree at that branch point
- the more recent the common ancestor, the more closely related the two species are
- common ancestors do not survive today- we cannot say that we evolved from the apes, or from the gorillas- we evolved from an ancestor that lift at some time in the past- happens that the gorillas also evolved from that same ancestor
21
Q
What did Linnaeus use to classify organisms, what is the issue with this
A
- observable features
- organisms adapt to their environments- possible for 2 unrelated species to adapt in similar ways- look very similar- convergent evolution - may be classified in same taxonomic group according to observable features
22
Q
What do we now use to classify organisms
A
- biological molecules
- certain large biological molecules present in all living things but have variation
- of we assume the earliest living things had identical versions of these molecules, the differences seen today are as a result of evolution
- organisms with similar molecules will be closely related as they haven’t evolved separately for long
- differences between the molecules in these species reflect the evolutionary relationships
- cytochrome C, DNA
23
Q
Describe cytochrome C as a way of classifying organisms
A
- protein used in process of respiration
- all living organisms that respire must contain cytochrome C, but it is not identical in all species
- amino acids in Cytochrome C can be identified- can compare AA sequences in samples of CC from different organisms
- if sequences are the same, the 2 species must be closely related
- if the 2 sequences are different, the 2 species are not so closely related
- the more differences found, the less closely related the species
24
Q
Describe DNA as a way of classifying organisms
A
- found in all living organisms
- DNA provides the genetic code- instructions for producing proteins
- code is same for all organisms- it is universal
- changes to the sequences of bases in DNA are called mutations- occur at random
- can compare DNA sequences to classify species
- the more similar the sequence in a part of the DNA, the more closely related the 2 species
- if there are many differences, the 2 species have evolved separately for a long time- can be considered less closely related
- probably the most accurate way to demonstrate how closely related one species is to another
25
What did Woese change about the classification system, why, what evidence did he use for this
- divided prokaryote kingdom into eubacteria and archaea
- based on face that bacteria are fundamentally to archaea and eukaryote- bacteria have:
- a different cell membrane structure
- flagella with a different internal structure
- different enzymes (RNA polymerase) for synthesising RNA
- no proteins bound to their genetic material
- different mechanisms for DNA replication and for synthesising RNA
26
What did Woese suggest about the relationship between archaea and eukaryotes
Share certain features:
- similar enzymes (RNA polymerase) for synthesising RNA
- similar mechanisms for DNA replication and synthesising RNA
- production of some proteins that bind to their DNA
Argued the eubacteria and archaebacteria are more different than archaea and eukaryotes- detailed study of ribosomal RNA gene- RNA and DNA are part of basic mechanism that translates genes into visible characteristics created 3 domain system
27
Who proposed the theory of natural selection?
Charles Darwin
28
Describe Darwins discoveries- what they were, how they were made, why they were commonly rejected
- Darwin was a naturalist who spent much of his life observing and studying living organisms
- the theory of evolution was not his idea- the idea that one species might evolve from another overtime was not knew, but Darwin suppose a mechanism for this process- natural selection- made it easier to believe in the theory of evolution
- also caused a certain amount of upheaval in Victorian Britain as it counted the religious beliefs of the time
- his ideas began to develop during a five year trip around the world in a ship called the HMS Beagle (1831
- during this trip he visited the galapagos islands where he discovered a large number of unusual species
- many of these species were similar to those found on the South American mainland
- what interested Darwin was that there was clear variation between the members of the same species found on different islands
- he also noted that what appeared to be a wide variety of bird species were actually all closely related finches- concluded that one species had arrived on the islands from the mainland and had then evolved to form many different species
29
Who was another scientists involved in the theory of natural selection, described this
Alfred Russel Wallace:
- another naturalist who independently came to the same conclusions as Darwin
- had made collections in both the Amazon and in South East Asia
- that first publications were joint papers on the subject of evolution by natural selection
- this was soon followed by Darwin's book, best known as 'the origin of species' (1859)
30
What were Darwins 4 particular observations
- offspring generally appear similar to their parents
- no two individuals are identical
- organisms have the ability to produce large numbers of offspring
- populations in nature tend to remain fairly stable in size
31
What did Darwin conclude from his observations
- realised that variation was the key to understanding how species change
- he saw that when too many young are produced, there is competition for food and resources
- as all the offspring are different, some may be better adapted than others
- the better adapted individuals obtain enough foods and survive long enough to reproduce
- these individuals can pass on their characteristics to the next generation- it therefore the population can change or evolve to become better suited to its environment
- summary- there is a struggle to survive- better adapted individuals survive and pass on their characteristics- over time, a number of changes may give rise to a new species
32
What are two types of evidence for evolution by natural selection
- fossil evidence
| - biological molecules
33
Describe fossil evidence as evidence for evolution by natural selection
Even in Darwin's time, known fossils clearly showed a number of interesting facts:
- in the past, the world was inhabited by species that were different from those present today
- old species have died out and new species have arisen
- the new species that have appeared are often similar to the older ones found in the same place
- Darwin was fascinated by the similarities that he found between species living today and fossil species
- began to understand that fossil species gave rise to more modern species, and he felt that this must be because the more modern species had variations that meant they were better adapted to the environment
- Darwin was also struck by the differences between the fossil species on the modern species- many of the fossil species were much larger found modern species come out but otherwise appeared very similar
- one of the most complete fossil records of evolution is that of the horse- the evolution of the modern horse can be followed through a sequence of species that are all very similar to each other- their similarity and their sequence in time provide evidence that one species arose from a previous one
34
Describe how biological molecules can be used as evidence for evolution via natural selection
Recent study of biological molecules provides very strong evidence for evolution:
- the fact that certain molecules are found throughout the living worlds is evidenced in itself- if one species gives rise to another, both are likely to have the same biological molecules- suggests that 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, the biological molecules are likely to differ more
- evidence from molecules such as cytochrome c and other proteins shows this pattern of change
- The structure of dna can be used in a similar way to that of cytochrome C
- genes can be compared by sequencing the bases in the DNA
- the greater the number of similarities between the gene sequences, the more closely related the species and the more recent their evolution
- it also shows that more distantly related species have more differences in their DNA
- comparison of human DNA with that of other organisms shows the following evolutionary relationships- 1.2% of our coding sequence is different from that of chimpanzees, 1.6% is different from that of gorillas, 6.6% is different from that of baboons
35
What is uniquely useful in tracing human history, describe this
- mitochondria contain their own DNA called mitochondrial DNA or mDNA
- during sexual reproduction mitochondria contained in the egg are passed to the offspring, therefore mDNA is passed on from the mother
- the history is not confused by DNA from the paternal line
- also, mDNA mutates more frequently than nuclear DNA as it does not have the same checking systems in place to proofread new copies
- therefore, there is plenty of variation in the sequence of mDNA between people from different parts of the world
- this variation can be used to solve outstanding uncertainties about the origins of different races- for example, it has shown that the polynesians migrated from South East Asia and that the Native Americans crossed from Siberia about 13,000 years ago rather than being descended from people in the Middle East
- the path of evolution seen in mitochondrial DNA is so clear that we can trace it back to a single female known as mitochondrial eve he lived in Africa about 150,000 years ago- whoever we are, and wherever we live, we are all her descendants
36
How does evolution work
- an individual that has a characteristic which helps it survive in its environment is more likely to live long enough to reproduce
- the process of evolution works by selecting individuals with particular adaptations to survive and reproduce highford at these adaptations are therefore passed from one generation to the next
- over a long period of time- possibly over many generations- morun small individuals in the population will have thoughts adaptive characteristic- we say that the adaptation has been selected
37
Describe how natural selection occurs
- mutation creates alternative versions of a gene- alleles
- this creates genetic variation between the individuals of a species- intraspecific variation
- once variety exists, then the environment can select- when resources are scarce the environment will select those variations- characteristics- that give an advantage- there is a selection pressure
- individuals with an advantagous characteristic will survive and reproduce
- therefore they pass on the advantageous characteristics- inheritance
- the next generation will have a higher proportion of individuals with the successful characteristics- over time, the group of organisms becomes well adapted to its environment- adaptation
fabrication must occur before evolution can take place- it is GENETIC variation that is important for evolution- variation due to environmental factors will not be passed on to offspring
38
What evolution is still going on today, name two examples
- whenever a species or a group of organisms is placed under a new selection pressure, different characteristics will be selected- evolution will occur
- this is most obvious in organisms that have a short life cycle
- pesticide resistance in insects, microorganisms
39
Describe pesticide resistance in insects in terms of natural selection, the issues with this
- some insects are pests- they eat our food crops, or cause damage to them, they can also act as vectors which transmits pathogens- humans have devised evermore ingenious ways to kill insects, but some insects always survive
- pesticides are chemicals designed to kill pests- insecticides specifically kill insects
- insecticides apply a very strong selection pressure
- if the individual insect is suspectible, then it will die
- if it has some form of resistance, then the individual may survive
- this will allow the individual with some resistance to reproduce on pause on the resistance characteristic, so the resistance quickly spreads through the whole population
- resistance to pesticides was first documented in 1914, when scale insects were found to be resistant to inorganic insecticides- as we have introduced new classes of insecticides such as cyclodienes, carbamates, formamidines, organophosphates and pyrethroids, cases of resistance have been documented within 20 years- resistance can arise within as little as two years
- when insects become resistant to pesticides, it's can lead to another problem- its cat cause the pesticide to accumulate in the food chain
- if insects are resistance, they survive applications of these chemicals- the insects may then be eaten by their predators- the predators receive a larger dose of the incesticide, and it is quite possible for the insecticide to move all the way up the food chain
- in this way, humans may receive quite large doses of insecticide
- because of increasing resistance and the fact that DTT accumulates in the food chain, it's husband bands in many areas, however it is still used in household spraying programmes in some countries
40
Describe microorganisms in terms of natural selection and evolution
- the use of antibiotics is a very powerful selection pressure on bacteria
- when you take antibiotics, most of the bacteria are killed
- but that may be one, or a few, that are resistant to the antibiotic
- they are rarely completely unaffected by the antibiotic, but they are more resistant than most
- once most of the bacteria have been killed, you tend to feel better, so many people stop taking the antibiotics before they have finished the prescribed course
- this allows the resistant bacteria to survive and reproduce to create a resistant strain of bacteria
- over use and incorrect use of antibiotics has led to strains of bacteria that are resistant to virtually all of the antibiotics in use
- some doctors now prescribed multiple antibiotics, this greatly reduces the chances that some bacteria will survive
- before selection, there is a variety of levels of resistance- this variation is caused by mutations that create genetic variation within the species
- directly after selection the least resistant individuals have been killed, all that remains are the individuals that possessed some level of resistance
- the population of partly resistant individuals reproduces- the next generation contains a much higher proportion of resistant individuals
- some bacteria have gained a particularly wide range of resistance- such as MRSA (meticillin-resistant staphylococcus aureus)- this bacterium has developed resistance to an ever increasing range of stronger and stronger drugs- this is an example of an evolutionary arms race- medical researchers are struggling to develop new and effective drugs, but the bacterial populations rapidly become resistant to them
41
Describe variation, describe 2 types, name 2 categories
- the presence of variety- differences between individuals- genetic or environmental
- intraspecific variation- variation between members of the same species- the greater genetic diversity of a species, the greater the intraspecific variation
- interspecific variation- differences between species- separates members of one species to another
- continuous and discontinuous
42
Describe continuous variation
- 2 extremes and a full range of intermediate values between those extremes
- most individuals close to mean
- number of individuals at extremes are low
- polygenic- often regulated by more than one gene
- can be influenced by environment in which organism lives
- usually quantitative data
- e.g. height in humans, length of leaves on oak tree, length of stalk on toadstall, number of flagella on bacteria
- plot on histogram or line graph
43
Describe discontinuous variation
- 2 or more distinct categories with no intermediate value
- may or may not be evenly distributed
- monogenic- usually regulated by single gene
- not influenced by environment in which organism lives
- usually qualitative
- bar chart
- e.g. gender, flagella or not, human blood groups
44
What are the different causes of variation
- inherited/genetic
- environmental
- combined effects
45
describe inherited/genetic variation
- the genes we inherit from our parents provide information that us used to define our characteristics
- the combination of alleles that we inherit is not the same ask that in any other living things unless we are an identical twin
- we may share many alleles with other members of our species, and we may 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 the same combination of alleles is remote- said the combination of characteristics that each of us possesses unique
46
describe environmental variation
- many characteristics can be affected by the environment- for example, and overfed pets will it become a beast, and a persons skin will turn and become darker with exposure to sunlight, trees being eaten by animals or cats, or growing in rock crevices- environments affects these things
47
describe how combined elements can affect variation
- environmental and genetic variation are not isolated- many characteristics are affected by both causes
- for example humans have become taller in the past century as a result of a better diet, but however good your diet is, you are unlikely to grow very tall if the rest of your family are short- height you can reach is limited by your genes
- not all of our genes are active at anyone time- for example puberty means different genes are becoming active- changes in the environment can also directly affect which genes are active
48
Why do we use statostiocal tests, name 3
- allow us to determine whether differences between figures ah a significant difference or simply natural variation
- standard deviation
- students t-test
- correlation coefficient- spearman's rank
49
What is standard deviation, what does a low and high one mean
- measure of variation- measures amount of variation/spread from the mean
- low S.D indicates that the data have a narrow range and the points are closely grouped to the mean- could indicate greater reliability
- high S.D- indicates data points have a larger range and are less well grouped- might indicate lower reliability
50
Standard deviation formula
51
How to interpret standard deviation results
- 68% should be within 1 S.D's of the mean
- 95% should be within 2 S.D's of the mean- anything outside this range might be viewed as anomalous
- 99% should be within 3 S.D's of the mean
52
what is the studnets t test, what do we do before working it out
- used to compare 2 means- tests whether difference between the 2 means is a significant difference
- first state a null hypothesis that there is no significant difference between the means of the 2 sets of data- t test tests whether we reject or accept this hypothesis
53
t-test formula
54
How to interpret t test results
- use degrees of freedom- number of values in a statistical calculation that are free to value- (sample size)-(number of data sets)
- can now use table of t-values- consider 5% significance level at certain degree of freedom
- if calculated t value is greater than the value at 5%, we can consider the difference between the 2 sets of data to be significant- reject null hypothesis
- if calculated t value is lower than the value at 5%, we can consider the difference between the 2 sets of data to be insignificant- accept null hypothesis
55
What is correlation coefficient/the spearman's rank
- used to consider the relationships between 2 sets of data
| - the spearman's rank tell us whether 2 sets of data are correlated or not
56
What is correlation coefficient/the spearman's rank
- used to consider the relationships between 2 sets of data
| - the spearman's rank tell us whether 2 sets of data are correlated or not
57
Speakmans rank formula
58
How to do the soearmans rank
- write null hypothesis- there is no relationship between x and y
- draw table- data set 1, rank 1, data set 2, rank 2, D (r1-r2), D^2
- rank both data sets from highest (1) to lowest (5/6/7 etc)
- take away rank 2 from rank 1 for each site
- square D values
- total all squared D values
59
How to interpret spearman's rank results
- find critical value for number of pairs of measurements
- if higher (incl. lower negative), reject null hypothesis
- there is a significant positive/negative relationship/correlation between x and y
- if lower (or higher negative) accept null hypothesis
60
What is an adaptation, what do they help with
- a characteristic that enhances survival in the habitat
- variation in species- variations that help organisms to survive are adaptations helps organism cope with environmental stresses and obtain the things they need to survive
61
Describe what a well-adapted organism will be able to do
- find enough food/ photosynthesise well
- find enough water
- gather enough nutrients
- defend itself from predators and disease
- survive physical conditions of environment- e.g. changes in temperature, light and water availability
- respond to changes in environment
- have sufficient energy to allow successful reproduction
62
What are/define different types of adaptation
- anatomical - structural- any structure that enhances survival
- behavioural- aspect of behaviour that helps organism survive conditions
- physiological/biochemical- adaptions that ensure correct functioning or cell process
63
Physiological adaptations of marram grass
- long roots- enables plant to reach water deep underground
- roots spread out over a wide area- enables Maram to absorb a lot of water when it is available helps stabilise sand dune in which plant lives
- leaves ar ecurled- helps reduce the surface area exposed to wind, traps air inside against lower epidermis so moisture can build up inside enclosed space
- lower epidermis is covered in hairs- reduces air movements so water vapour is retained close to the lower epidermis
- lower epidermis is folded to create pits in which the stomata are positioned- water vapour builds up in pits reducing loss of water vapour from inside the leaf
- lower density of stomata- less water vapour is lost
- leaf covered in thick waxy cuticle- reduces evapouration from cells of leaf
64
Examples of behavioural adaptations- worms, marams
- when you touch an earthworm, it quickly contracts and withdraws into its burrow- avoids being eaten when anything touches as has no eyes
- marram grass responds to shortage of water by rolling leaf more tightly and closing stomata- reduces transpiration. When covered in sand, will grow quickly to reach sunlight
65
Examples of physiological/biochemical adaptations- yeast, marram
- yeast saccharomyces- respire sugars anaerobically or aerobically depending on how much oxygen available
Marram:
- ability to roll leaf due to specialised hinge cells in lower epidermis- loose water when water is scarce- loose turgidity- rolls leaf more tightly. When more water is available, hinge cells become turdgid, opening up the leaf to allow easier access to carbon dioxide for photosynthesis
- guard cells work in similar way-open and close stomata- non-turgid cells close stomata and turgid cels open somata
- not very salt toldernat but maintains cell water potential that is lower than other plants- enables to survive in salty conditions found beside sea
- leaves contain many lignified cells that provide support when turgidity is lost- keeps leaf upright when water is not available
66
What is convergent evolution
the process whereby organisms not closely related independently evolve similar traits as a result of being exposed to similar environments or ecological niches
67
Describe an example of convergent evolution
- Marsupial and placental moles
- mole is a burrowing animal that feeds on small animals in the soil
- marsupial moles live in Australia and are part of a group of mammals that have been evolving separately from placental mammals for up to 100 million years
- despite this separate evolution and bing unrelated, marsupial and placental mols share a number of characteristics and look remarkable similar- they have:
- cylindrical body
- small eyes
- strong front legs
- large claws on front legs
- short due
- short tail
- nose with tough skin for protection
Decks in class (3)
# Cards
