IB Biology Flashcards
Exam
A1.1.1 Water as the medium for life
Evolution of the first cell could not begin until temperature cooled enough for water to form and later, for the water cycle to begin. It is thought the first cells slowly evolved in the oceans. A solvent is needed for reaction to occur. First cells evolved a membrane to separate the water in the cytoplasm from the “ocean water”. Water is a solvent that: makes up fluid in cells, permits transport, essential to blood and other fluids in organisms, provides medium for life.
A1.1.2 - Hydrogen bonds as a consequence of the polar covalent bonds within water molecules
Covalent bonds - two atoms share electrons. Equal sharing of electrons creates a non-polar covalent bond. (neither has a higher density) Polar covalent bonds are unequal sharing of electrons. (different charges at each end) Ephemeral attraction = a hydrogen bond.
A1.1.3 - Cohesion of water molecules
Water molecules are highly cohesive. Cohesion = same molecules attracted to each other. Two water molecules bonded together = a hydrogen bond. At waters freezing point, molecular motion slows the the point where the hydrogen bonds become locked in place into crystal ice forms. Ephemeral hydrogen bonds between liquid water molecules is why water has surface tension. Surface tension = the layer of water molecules at the surface of a body of water which does not have water molecules above it. Water moves up a water column through xylem. Water then evaporates through transpiration and the water leaving has cohesion. There is then tension due to the low pressure caused by the evaporation so all water moves up the leaf. (occurs in stomata)
A1.1.4 - Adhesion between the water and other polar substances
Attraction between to unlike molecules due to hydrogen bonding = adhesion. Adhesion keeps the column within the water column from dropping down the tube. (same in capillary tubes) Capillary action in soil acts similar to capillary tubes. Water molecules adhere to the polar molecules making soil and water molecules move up through cohesion.
A1.1.5 - The solvent properties of water
Any solution that has water as the solve = an aqueous solution. Any substance that dissolves readily in water is hydrophilic. Any that does not is hydrophobic. Water can transport dissolved substances and many substances are an aqueous solution . hydrophobic (insoluble) are found in steroid hormones - passes directly through he plasma membrane. And proteins. Epidermal cells of leaves secrete a way that coats leaves (the cuticle) and is a water barrier - without this leaves would dehydrate as they are often exposed to the sun.
A1.1.6 - The physical properties of water
Table 1 come back and complete this
A1.1.7 - The origin of water on Earth (HL)
Most water remains as liquid. Our planet has a gravitational pull to retain water on or near its surface due its size. Some water that helps form our planet is trapped deep in the crust. Water molecules exist in 2 forms. Difference exists due to number of neutrons. “Ordinary” hydrogen atoms exist in water without any neutrons. “Heavy water” contains atoms with a neutron. This hydrogen is called deuterium. All bodies of water contain both of these, with the typical water being more common.The ratio of hydrogen to deuterium is similar tot he ratio on many asteroids. A theory is that the Earth used to only be made of magma but as asteroids struck the earth they brought hydrated minerals that became the earths crust.
A1.1.8 - The search for extraterrestrial life
Goldilocks zone = Earth being in position with the sun that allows water to be in its liquid form.
A1.2.1 - DNA is the universal genetic material
DNA provides long term genetic information for all organisms on Earth. Mutations occur in DNA and pass on to the next generation. DNA is universal providing evidence for our common ancestry. Sequences of nitrogenous bases are genetic messages/genes. Messages code for amino acids. Amino acids build proteins - cells identity + function is determined by the proteins ability to synthesize. every cell in a multicellular organism has the same DNA, but each uses only genetic info. that retains ofr that cell.
A1.2.2 - The structure of nucleotides
DNA + RNA are polymers of nucleotides. - has repeating units called nucleotides within the much larger molecule. Nucleotides = One phosphate group, one five-carbo monosaccharide (pentose sugar) and a nitrogenous base. Covalent bonds occur to produce the functional unit.
A1.2.3 - Sugar to phosphate “backbone” of DNA and RNA
The pentose sugar of one nucleotide is covalently bonded to the phosphate group of the next nucleotide. Nucleotides bond together to form a polymer as a result of condensation reactions forming covalent bonds between the sugar and phosphate group of the next. These bonds take a lot of energy to break so the nucleic acid polymer made of nucleotides is stable.
A1.2.4 - Nitrogenous bases within nucleic acids
4 bases in RNA + 4 in DNA. RNA has uracil instead of thymine. RNA = ribose, DNA = deoxyribose.
A1.2.5 - The structure of RNA
RNA = nucleotides bonded tog. in specific sequences. Nucleotides join through a condensation reaction between the pentose sugar of 1 nucleotide + the phosphate group of the next nucleotide. This reaction releases a water molecule. (If RNA molecule contains 322 nucleotides, 321 molecules of water were produced in its synthesis - 321 condensation reactions formed.)
A1.2.6 - The structure of DNA
RNA = single chain of nucleotides. DNA = 2 strands of nucleotides connected through hydrogen bonds. Two bases making up 1 rung = complimentary base pairs.
A1.2.7 - Distinguishing between DNA and RNA
DNA + RNA = linear polymers w/ sugars phosphates + bases. Note the differences in the two on the table. Ribose has a molecular formula of C₅H₁₀O₅, Deoxyribose = C₅H₁₀O₄. When removing 1 oxygen from the alcohol (-OH) group, it shifts the formula by a lot. mRNA = synthesized from a gene. IT leaves the nucleus and represents the genetic info. necessary to make a protein. tRNA- when a specific protein is synthesized, specific amino acids must be added to the amino acid chain in an order. tRNA transfers the correct amino acid into a growing chain of amino acids. rRNA - created ribosomes. ATP single- nucleotide nucleic acid. Produces a chemical energy. When a muscle contracts, ATP molecules are used as an energy source for the movement.
A1.2.8 - The importance of complementary base pairing
Allows for templates of DNA to be made so the DNA can be synthesized.
A1.2.9 - Storage of genetic information
DNA stores its info. in its bases. Every three bases is called a triplet codon - w/ a meaningful piece of info. There are 4 diff. nucleotides that can be arranged in triplets. The odds of Dan containing any 1 triplet is 1/64. This shows the info. is limitless and enormous. The likelihood that 2 DNA molecules are identical as a result of random chance is nearly 0.
A1.2.10 - Genetic uniqueness
Genetic code has remained unchanged due to evolution. Evolution changes DNA sequences slowly but always uses the same mechanisms of genetic coding.
A1.2.11 - Directionality of RNA and DNA strands (HL)
The 5’ and 3’ = fifth and third carbon atoms. DNA has 2 strands antiparallel. - One runs 5’ to 3’ other is 3’ to 5’. Both are synthesized 5’ to 3’. When RNA/DNA is formed, 1 nucleotide at a time is added to the molecule. A new strand will always begin with the 5’ end.
A1.2.12 - Purine-to-pyrimidine bonding
When bonding, a purine is bonded to a pyrimidine and results in a consistent strand. Purine = double ringed, pyrimidine = single ringed. This makes a very stable helix shape with three dimensions.
A1.2.13 - Efficient packaging of DNA molecules
DNA is long so there is a packaging solution. Histones are proteins. DNA wraps itself around 8 histones w/ an additional histone holding the structure tog. This results in a nucleosome. DNA extends from one to the other then stack up in an organized pattern, coiling other proteins in a condensed shape. The overall shape is a chromosome. Humans have 46 of these.
A1.2.14 - The Hershey-Chase experiment
Hershey and Chase made use of radioisotopes w/ radioactive isotope labelling. They can be detected w/ in molecules. One culture had radioactive phosphorus 32. This virus produced detectable P32. Another was sulfur 35. This was present in the outer coat of the viruses produced. Dan does not include suffer and suffer was only detectable in the protein shell of the virus because 2 of the 20 amino acids that can be present in protein contain sulfur. they were each allowed to infect the bacterium E. coli. The E. cold infected with the sulfer had no radioactivity inside the cell. the P had radioactivity detected. DNA contains P and not S so they concluded DNA was the genetic material.
A1.2.15 - Chargaff’s rule
Scientists believed protein was responsible for genetic traits. Chargaff developed a research technique to show proportions of nitrogenous base types found in DNA. The results showed there is almost the same ratio of adenine to thymine and gunanine to cytosine. DNA contains the same # of adenine as thymine + guanine and cytosine. This is known as Chargaffs rule. Shows the tetra nucleotide theory is false, as all would ne equal, but there was not equal proportions.
A2.1.1 - The formation of carbon compounds
Larger mass has more gravity than smaller. The number of impacts on Earth’s surface began to decrease 4 billion years ago. Free oxygen was not present, if it had been it would have formed a layer of ozone in the upper regions of the atmosphere - blocking UV light. It is thought Earth’s early atmospheric components coupled w/ high surface temperatures, lighting w/ gradual cooling which resulted in formation of many carbon compounds. This is not evident today.
A2.1.2 - Functions of life
Metabolism includes all chemical reactions that occur w/in the organism. Due to this, cells can convert energy from one form to another. Growth may be limited but is always present. Reproduction involves hereditary molecules that can be passed to offspring. Responding to stimuli in the environment allow organisms to survive. Homeostasis = maintenance of a constant internal environment. Using sources of compounds w/ many chemical bonds that can be broken down to provide energy is the basis of nutrition. Excretion is essential as it allows chemical compounds that are harmful to be released. Cell theory has 3 main principles - all organisms are composed of one or more cells, cells are the smallest unit of life, all cells come from pre-existing cells.
A2.1.3 - Evolution of the cell
The third principle of the cell theory = cells may only come from other pre-existing cells. Protocells = appear is pre-biotic environment so more complex cells could form. A series of them. + physical processes have to occur for a cell to evolve. 1. Synthesis of small carbon compounds from abiotic molecules. 2. Small organic molecules joining from large-chain molecules (polymers) 3. Polymers becoming contained by membranes, creating a protective homeostatic environment around the polymers - separate from surroundings. 4. Development of self-replicating molecules - inheritance and control can occur.
A2.1.4 - Inorganic to carbon compounds
Inorganic compounds do not contain carbon (unless CO2) Carbon compounds contain carbon are complex. These make life possible. The Miller-Urey experiment was to stimulate the conditions thought to be on Earth + to determine if these gases could interact to produce the first stage in the evolution life. The apparatus was charged w/ the simple inorganic compound CH4, NH3 and H2 representing Earth’s early atmosphere. Heat was used to produce water vapour which rises to the chamber holding the inorganic compounds. 2 electrodes in this chamber produce 7,500 volts + 30 amps of electricity, representing lightning. Cold water flows into the condenser to allow condensation of gaseous compounds. a sample is collected for analysis. Miller identified several simple organic molecules known as organisms - hydrocarbons and amino acids. Primordial soup was found (sea of simple organic molecules) It is believed that this is invalid as they believe the first atmosphere of our planet formed slowly over extended periods of time from volcano gases. This means our chemical properties on Earth are not the same as before and gases today do not contain NH4/CH4. Instead H2O vapour. CO2, SO2, + CO + HS4. These would produce a non-reducing environment and the one in this experiment produced a reducing environment.
A2.1.5 - The formation of vesicles
Membrane provides a barrier between the inside of the cell w/ surrounding environment. Fatty acids were thought to be present in early Earth. These were present in water + has polarity. 1 end = hydrophilic other = hydrophobic. When large #’s are placed in H2O, they organize into small cell-sized double-layer bubbles called vesicles. Development of a boundary around a vesicle = compartmentalization = was necessary for formation of first cells. As they progressed this compartmentalization became evident w/in the boundary allowing specialization of functions in diff. regions inside the outer protective fatty acid bilayer.
A2.1.6 - RNA as the first genetic material
Short RNA molecules = assemble spontaneously from nucleotides, can form copies of itself so a type of genetic material, demonstrates the ability to control chem. reactions so acts as an enzymatic role. These allowed the functions necessary for the formation of early cells. Ribozymes (type of RNA) is active in catalysing activities - faster development of peptide bonds. Because RNA is so much simpler than DNA it is thought to have been the first genetic and controlling compound of a living cell.
A2.1.7 - Evidence for a last universal common ancestor (LUCA)
- universal genetic code by DNA + shared by all cells. - over 300 genes common to all cells. - same building blocks for both DNA + RNA in all cells. - common molecular processes w/in all cells (replication of DNA + production of proteins) Hypothesized that other life forms having distinctive characteristics other than these have evolved but are not present today due to unsuccessful comp. w/ LUCA + its descendants.
A2.1.8 - Dating the first living cells and LUCA
Charles Darwin utilized the concept of common ancestry. Everything traces back to a single ancestor, the LUCA. Earliest evidence of life on Earth comes from fossils. Most are hard parts (bones/teeth) but some can be footprints etc. Estimated that life occurred earliest on Earth 3.5 billion years ago. An accurate means of dating fossils involve radiometric techniques - based on the half-life, length of time it takes for a half a radioactive isotope to change into another stable element. Fossils contain isotopes. SO by measuring the amount of an isotope in a fossil + comparing it w/ the amount taken up when the organism lived, we can determine the age of the fossil. This is absolute dating of a fossil’s age. Relative dating is not as exact as absolute darting. It utilizes sediment layers of Earth + index fossils.
A2.1.9 - Hydrothermal vents and the evolution of the LUCA
A hypothesis suggests that the location for the origin of life on earth is around hydrothermal vents. Lot’s of life exists at the bottom of the ocean even w/ no sunlight. This gives credibility to the hypothesis that the earliest life forms could have formed deep in the ocean around hydrothermal vents. Evidence for LUCA at hydrothermal vents = very old fossilized precipitates originated here, commonality of genetic sequences in the organism near the vents - likely single ancestor, presence of mineral-rich environment necessary for chem. reactions, presence of H2 and CO2 results in the reducing environment essential for carbon compound formation.
A2.2.1 - Cells and the functions of life
Cytology = studies all facets of the cell. Cell theory = all organisms are composed of 1 or more cells, cells are the smallest units of life, all cells come from pre-existing cells.
A2.2.2 - Cells and the microscope
Cells need to be observed w/ high magnification + resolution. Light microscopes use light passing through to form an image, electron microscopes use electrons passing through a specimen to form an image. Magnification = measured size of image/actual size of specimen.
A2.2.3 - Advanced microscopy
SEM uses a beam of electrons to scan the surface of a specimen. TEM aims a beam of electrons through a thin section of a specimen - inner structure is viewed. Freeze fracture = rapid freezing of a specimen followed by physically breaking the specimen apart. This reveals a plane through the sample that is examined. Cyrogenic electron microscopy enables an image to be formed using computer enhancement that shows three-dimensional framework of proteins involved in the function of a cell. Light microscopy involves fluorescent stains and immunofluorescence that combine w/ specific cellular components. The condenser on a light microscope posses a lens that directs light rays from the light source through the specimen.
A2.2.4 - Structures common to all cells
All cells posses certain common structures including - DNA as their genetic material, a cytoplasm composed of mainly water, a plasma membrane composed of lipids that surrounds the cytoplasm. For new cells to be formed from pre-existing cells, they must store and transfer info. DNA fulfils this role due to tis ability to form large molecules from nucleotides. The mainly water part of the cytoplasm = cytosol which contains all ingredients for the cell to function. The plasma membrane encloses the cell + protects its contents w/ 2 layers of lipids combined a s a bilayer.
A2.2.5 - The prokaryote cell
Prokaryotic cells = small + bacteria cells. Their cell wall is composed of a carb-protein complex called peptidoglycan. Some has an additional layer of a polysaccharide outside the cell wall called the capsule. This allows adherence to structures like teeth, skin and food.
A2.2.6 - The eukaryote cell
The comparison between prokaryotic and eukaryotic cells are - prokaryotic cells = DNA in a ring form w/ out protein, DNA free in the cytoplasm, no mitochondria, 70s ribosomes, no internal compartmentalization to form organelles. Eukaryotic cells = DNA w/ proteins as chromosomes, DNA enclosed w/ in a nuclear envelope (nucleus), mitochondria is present, 80s ribosomes, internal compartmentalization present. Both have an outside boundary that always involves a plasma membrane, both cells conduct all functions of life, DNA is present in both.
A2.2.7 - Unicellular organisms
Metabolism = sum of all chem. reactions that occur w/ in an organism. Growth = The development of an organism. Reproduction = ability to produce offspring. Response to stimuli = As the environment changes, the organism adapts. Homeostasis = maintenance of a constant internal environment. Nutrition = the ability to acquire the energy + materials needed to maintain life. Excretion = the ability to release materials not needed into the environment. Movement = ability to change position. Unicellular have unique ways of carrying out life functions compared to multicellular organisms.
A2.2.8 - Different types of eukaryotic cells
All 3 cell types contain mitochondria that posses cirstae, a matrix + a double membrane. In all 3 the mitochondria functions in the proaction of ATP.
A2.2.9 - Atypical eukaryotes
Some multicellular fungi produce filaments called hyphae. Phloem sieve tube have a specialized function allowing transportation w/ in a multicellular plant. These elements have one walls ww/ pores + has min. cellular components. These can only remain alive w/ the help of companion cells - maintain a close connection w/ sieve tube elements.
A2.2.12 - The origin of eukaryotic cells (HL)
Endosymbiotic theory = about 2 billion years ago a larger cell w/ a nucleus did sexual reproduction + engulfed a smaller prokaryotic cell that could produce energy, these cells developed a symbiotic relationship forming 1 single organism, the smaller engulfed cell went through multiple changes to become a mitochondrion. The larger cell helped the bacteria prokaryote by protecting it + providing carbon compounds. Much more evidence for this exists.
A2.2.13 + A2.2.14 - Cell specialization + multicellularity
Compartmentalization was an important process in the development of the cell. All cells in multicellular organisms have the same genetic info. For specialization + differentiation to occur, mechanisms have developed that control + coordinate gene expression.
A2.3.1 - Characteristics of viruses
Viruses are all small and fixed, contain a nucleic acid (RNA or DNA), enclosed by a boundary composed of a protein - capsid, do not contain cytoplasm inside the capsid, possess few enzymes. They infect a host cell - the capsid allows attachment to the host cells. The host cell is the cell that a virus uses to carry out its metabolic +reproductive functions. Some viruses contain a capsid w/ a specialized protein that allows the genetic material of the virus to penetrate the host cell membrane. Some viruses have an envelope outside their protein boundary from the host cell’s plasma membrane.
A2.3.2 - Structural diversity in viruses
Electron microscopes are needed to view viruses. Viruses show great variation in shape + structure. They can be thread, polyhedral or spherical.
A2.3.3 + A2.3.4 - The life cycle of viruses
Viruses must have a host cell. To reproduce: attach to a site on a host cell, then incorporate their genetic material into the cytoplasm of the most cell, then use the host cell’s processes to produce components of themselves, then assemble the viral components unto new functioning virus entitles, finally release the new virus entities into the host cell’s environment. Bacteriophages - viruses which infect bacteria. The lytic life cycle is new virus particles are released by the lysis or rupturing of the cell membrane by the enzyme lysozyme. Lysis only occurs after the production of fully functional virus particles - virions. The lysogenic cycle: DNA of bacteriophage combines with the bacterial DNA to form a prophage. The next generation carries the prophage in their genome.
A2.3.5 - The origin of viruses
The diversity of viruses suggest several possible origins. They share an extreme form of obligate parasitism as a mode of existence so the structural features that they have in common could be regarded as convergent evolution. The genetic code is shared between viruses and living organisms. Virus first hypothesisL viruses originated before cells. Regressive hypothesis: viruses were once small cells that became parasites of larger cells. Escape hypothesis: DNA and RNA escaped from larger organisms such as bacteria.
A2.3.6 - Rapidly evolving viruses
Influenza and HIV are two types of virus which display rapid rates of evolution. HIV goes through genetic drift at a very rapid pace. When treating these caused by rapidly evolving viruses they may start to resist treatment.
A3.1.1 - Variation between organisms
Organisms are categorized based on morphology (physical appearance) Each category is called a taxon. Largest taxon is a “domain” + contains all the specific taxa - KPCOFGS. When variation can be placed into categories it = discontinuous. when there is a range = continuous.
A3.1.2 - Species as groups of organisms
Linnaeus had difficulty identifying p;ants so he put known living organisms and placed them into categories. This morphological classification is still used today such as Elephas maximus.
A3.1.3 - The binomial naming system
Binomial nomenclature = system of naming organisms by using 2 names. First name is always capitalized while second is lowercase + genus + refers to the species. Both are written in italics or underlined when written. Species in the same genus have similar traits.
A3.1.4 - Biological species
Biological species concept - to be classified in the same species, they must be able to breed together + produce fertile offspring. The challenges w/ this include the fact of some organisms reproducing asexually so do not breed, some hybrids produce fertile offspring. Other definitions include the ecological niche of an organism, genetics types of molecules an organism produces, lineage for extinct species.
A3.1.5 - Distinguishing between populations and species
Speciation = process of population being operated into 2 groups that cannot reproduce together. 1 can have mutations or other pressures causing it to evolve differently. There are now 2 species that have a common ancestor.
A3.1.6 - Diversity in chromosome numbers
Different species have different chromosomes numbers. Diploid cells always have an even number of chromosomes as it must be divisible for offspring.
A3.1.7 - Karyotypes
Karyogram = representation of chromosomes in a cell arranged in a format - placed in order of size + shape. Shape depends mainly on the position of the centromere. Cells are stained on a glass slide, photomicrograph is obtained during metaphase, images are cut out + separated, images of each pair of chromosomes are placed in order of size + shape. Evolution of chromosome 2 = scientists have made 2 hypotheses as to why humans have 46 and chimpanzees have 48 chromosomes = a complete chromosome disappeared / 2 chromosomes from an earlier common ancestor fused to become 1 chromosome. To test this, we can examine 2 characteristics that help identify a chromosome: shape + banding patterns. An X shape chromosome = metacentric. If 1 centromere is at 1 end + arm is much shorter than the other it is an afrocentric shape. All primates have both. A hypothesis is that human chromosome 2 arose from the fusion of shared ancestor chromosomes 12 + 13. Chromosome 2 was compared to the chimp. 12 + 13 and the 2 acrocentric non-human chromosomes were placed end to end + have a similar length to the human chromosome. The centromeres lined up w/ 12 but not 13. This refutes the hypothesis. DNA w/ in the centromere is called satellite DNA. Telomeres are caps on tips of chromosomes that contain repeating sequences of DNA. There is telomeric DNA in the centre of human chromosome 2. This is not supposed to be in the centre but only at the tups and is present where the 2 chromosomes would have fused. This provides evidence.
A3.1.8 - Unity and diversity of genomes
Variations of the genome causes mutations. a variation involving 1 base is called a single nucleotide polymorphism. Only 5% of SNPs are functional (make a difference) Most will not affect the phenotype. The Human Genome Project aimed to determine the order of all bases in the human genome. Genome = all genetic info. of an organism. Organisms in the same species share most of their genome but variations give some diversity.
A3.1.9 - Eukaryote genomes
A major difference between genomes is their size: quantity of DNA in the nuclei. Certain species need genes to do specific things. A specific way to compare genetic diversity in eukaryotes is to look at mitochondrial DNA.
A3.1.10 - Genome sizes
Genome size can indicate complexity but there are exceptions to conclude this is not a reliable indicator.
A3.1.11 - Whole genome sequencing
Phylogenetics = comparison of whole genome sequences. Organisms that share similar genomes are more closely related than others that aren’t. Next-generation sequencing techniques = mix of lab hardware, chem. markers that allows for private citizens to get their genomes sequences. Some countries have this as illegal. Personalized medicine is info. about a persons genetic makeup being applied to an individual when prescribing treatments. Knowing more about how a patient’s genome might cause new proteins to be produced in their cells/ trigger certain genes to be turned on/off may lead to breakthroughs in medical treatments. Another use of the human genome is production of new medications - they must find beneficial molecules that are produced naturally in healthy people, find out which gene controls synthesis of a desirable molecule, copy that gene + use it to instruct synthesis of a molecule in a lab., distribute the beneficial therapeutic protein as a new treatment.
A3.1.12 - Difficulties with the biological species concept
Parthenogenesis = process of females producing a young w/ out a male. In plants a similar process occurs = vegetative propagation (strawberry plant sends out a runner that takes root near original plant. Bacteria reproduces asexually using binary fission. Bacteria undergoes horizontal gene transfer. An assumption of the concept of a species is all members of the species has a common lineage from common ancestors. This is the basis of the tree of life concept. Xenologs/jumping genes are sequences of DNA that is found in common w/ another species than the one it is found in.
A3.1.13 - Chromosome number as a shared traut
A female horse +make donkey can mate and produce a mule. Mules cannot mate to make more mules. Because mules are not fertile, the mule is not a new species but an interspecific hybrid. This is because a female horse has 64 chromosomes while a donkey has 62 creating 63 in the offspring which is nit divisible by 2.
A3.1.14 - Dichotomous keys
Dichotomous key is used to establish which taxa an organism belongs to.
A3.1.15 - DNA barcoding
Genetic sequences are obtained from organisms + given a number that is matched against a database of sequences that are previously identified + named organisms. A DNA barcode is a short sequence of DNA inside an organism cells that can be used to quickly identify the species. Environmental DNA is collected from the environment rather than the organism. The DNA is amplified using a technique called polymerase chain reaction. Scientists studying zones w/ pollution want to know the biodiversity and if it’s affected. This is measured by counting the number of species present. Species can be used as bioindicators which are so sensitive to pollution that their presence indicates a lack of pollution, and conversely. Disadvantages of using environmental DNA includes it only giving an indication of the presence/ absence of a species, not the size. DNA does not indicate if it is from a li ing organism or a dead one. Certain chemical incompatibilities exist w/ processing of soil samples due to substances in the soil interfering w/ the sequencing process - inaccurate results possible.
A4.1.1 - Evolution
Darwin came up w/ the theory of evolution by natural selection. Evolution is defined as the process of cumulative change in the heritable characteristics of a population. DNA evidence provided new support for natural selection + led to the modern synthesis theory. Darwin + Wallace’s theory replaces a previous idea by Lamarck. This was that organisms acquired characteristics through their lifetime + passed them on to their offspring.
A4.1.2 - Biochemical evidence for evolution
Our DNA includes genes that go back to common ancestry w/ fish. This explains during the development of human embryos we have slits in our necks (fish). A phylogenetic can be used.
A4.1.3 - Selective breeding
Selective breeding = breeders choose desirable traits + breed them together. Breeders choose which animals will reproduce + which will not = artificial selection.
A4.1.4 - Homologous and analogous structures
Homologous structures = derived from the same body part of a common ancestor. Pentadactyl limbs are a common ex. for this. Analogous structures = same function but different body part so no common ancestor. Wings are a common ex. of this.
A4.1.5 - Convergent evolution
Analogous structures provide evidence for evolution. Convergent a + divergent evolution refers to not only an entire organism but also to physical features. Convergent evolution = diff. species look / behave more like each other over time potentially allowing them to exploit similar niches + developing analogous structures.
A4.1.6 - Speciation
New species are formed due to speciation. For ex. the island iguana populations - they have evolved differently over years as they have had to adapt to differing environments. When they can no longer interbreed like the mainland iguanas + the island iguanas, a speciation split has occurred. Extinction happens when the last individuals of a species die out. (Wooly mammoth, dodo, T. Rex)
A4.1.7 - Reproductive isolation and differential selection
Some species may be prevented from reproducing due to a barrier between them - temporal geographical or behavioural. Over time 2 populations will face selection pressures so will change. Eventually they will change into 2 separate populations. This is reproductive isolation. An example of this is the Bonobos living south of the Congo river while the chimpanzees live on the north + east of the river. Due to the difference in habitat, food and enemies their traits differ from each other. Chimps. are more aggressive bonobos are more peaceful.
A4.1.8 - Allopatric and sympatric speciation
When a new species forms from an existing species due to a barrier = allopatric speciation. (geographical speciation leads to this) Sympatric speciation is a new species forming from an existing species living in the same geographical area. This can be caused by temporal / behavioural isolation. Temporal isolation = incompatible time frames that prevents gametes from touching, Ex. if female parts of flowers of 1 population of plants reach maturity earlier than realize of pollen of another, 2 cannot create offspring. Behavioural isolation is differing behaviour isolating it from the rest of the pop.
A4.1.9 - Adaptive radiation
Adaptive radiation = similar but distinct species evolved rapidly from a single species. This happens due to variation w/ in a pop. A niche is a position / role in a community. Through natural selection + presence of reproductive isolation, a new species can evolve.
A4.1.10 - Barriers to hybridization, and hybrid sterility
when a sperm fertilizes an egg, its chromosome 1 needs to be compatible w/ the eggs chromosome 1. Each gene’s position, its locus needs to match for the genetic info. to contribute to the offspring. Behavioural isolation happens when 1 populations lifestyle is not compatible w/ another pop. Females of 2 species will not be attracted by courtship rituals performed by males of a diff. species. Hybridization will then not take place + their gene pools will not mix.
A4.1.11 - Abrupt speciation in plants
Polyploidy = a cell contains 3 or more sets of chromosomes. This can arise during production of sex cells. Much more common in plants than animals. In plants this can lead to more vigorous plants that produce bigger fruits or food storage organs. In animals this is normally fatal but some fish and frogs demonstrate polyploidy. But the change causes the offspring w/ the original pop. to be impossible so speciation occurs. An advantage to polyploidy is that it can allow sterile hybrid plants to be fertile. W/ additional genetic material, plants can produce seeds + pollen w/ the same number of chromosomes which can produce fertile offspring. Extra genetic material can give plants an advantage over other plants. Abrupt speciation = hybridization + polyploidy can allow speciation to be very quick. The new organism has a diff. chromosomes number from its parents so is reproductively isolated.
A4.2.1 - Biodiversity exists in many forms
Biodiversity = variety of life in an area, A healthy coral reed = high level of biodiversity - burned forest does not. Ecosystem diversity = diversity from largest viewpoint. Great Barrier Reed is an ex. of 1 of the most ecologically diverse locations. Species diversity or species richness is the number of diff. species in a community. Species evenness is a measure of the relative abundance of each species in the community. Populations w/ greater genetic diversity are more stable.
A4.2.2 - Has biodiversity changed over time?
Even though extinction is very high, fossil record suggests there are more species alive today than ever. There are still many more species to be discovered.
A4.2.3 - Human activities and the rate of species extinction
Extinction caused by humans = anthropogenic species extinction. An extinct species Case study 1: North Island giant Mao lived in New Zealand. They were hunted to extinction so this is anthropogenic extinction. Case study 2 : Caribbean monk seals were killed for its oil.
A4.2.4 - Human activities and ecosystem loss
Case study 1: mixed dipterocarp forests were dominated
A4.2.5 - A biodiversity crisis
IPBES provides guidance for reliable scientific policymakers, IUCN was continuously updated for its list of threatened species.
A4.2.6 - Causes of the biodiversity crisis
Human pop. growth affects include; over-exploitation of resources, hunting, deforestation, monoculture, pollution, increased pest species, invasive species, urbanization, spread of disease.
A4.2.7 - conservation of biodiversity
In situ conservation efforts - managing natural areas. Ex situ conservation efforts- managing 1 or more species outside their natural area. There is reqildign, reclamation of degraded landscapes, and establishment of nationals parks that is an attempt at ex situ conservation. Ex situ efforts include animal husbandry, artificial insemination. Botanic gardens help promote biodiversity. Seed banks safely store seeds. Animal tissue banks - germplasm stores reproductive cells of various threatened species. second type is somatic tissue + used for DNA research + possible cloning.
A4.2.8 - The EDGE of existence programme
First IUCN Red list is consulted. A score is generated from this list to how endangered the species is. Then is evaluated for its unique evolutionary history. Done using DNA sequencing info.
A3.2.1 - The classification of organisms
Classifying organisms helps us discover ancestries + see which species are related to + how all species are connected.
A3.2.2 - Difficulties in classifying organisms
Difficulty of Linnaeus’s system is the concept of hierarchy whereby a smaller category is placed w/ in a bigger category. If an organism belongs to a genus it must be in the sam family as all other organisms in that genus. The more that organisms are discovered, the more often the hierarchy does not work. Introgression = process which hybrids form over many organizations but have an equal share of the original two species genetic info. there is an unequal contribution from each species. Some variety in wolves can be explained by introgression with coyotes.
A3.2.3 - Classification using evolutionary relationships
Classifying organisms using molecular differences in protein sequences + DNA = molecular systematics. Phylogeny is the study if evolutionary past of a species. Comparing the phylogenetic tree shows the evolutionary relationships between species by showing which species developed from a common ancestor. The advantages of a system = not based on contrived categories. Evolutionary relationships can looked at w/ clades / monophyletic groups. - a group compromising the most recent common ancestor of that group = its descendant. A clade compromise just 1 species or can be made up of multiple species.
A3.2.4 - Clades display common ancestries and shared characteristics
Cladistics is a natural classification of taxa grouping. Primitive traits (plesiomorphic traits) have similar structure + function + evolved early in history. Derived traits (apomorphic traits) have similar structure + functions have evolved more recently in the form of modifications of a previous trait. The resulting classification shows that all the organisms descended from the earliest common ancestor being studied have the primitive trait but in smaller clades some would have derived traits. In another clade, that considers more species, a primitive trait could be considered a derived trait. By comparing these characteristics, the quantitative results indicate which organisms have undergone a more recent split.
A3.2.5 - The evolutionary clock
Differences in polypeptide sequences accumulate over time as mutations occur. We can count differences in homologous molecules from 2 related species to quantify similarities + differences through DNA hybridization. A strand of DNA is taken from a species + a homologous strand from another species which are then fused tog. using enzymes. Another method uses quantitative biochemical data as a molecular clock to estimate time of speciation events. We cannot think of this as an actual clock as mutations can occur at varying rates so we only have averages.
A3.2.6 - Constructing cladograms
A cladogram is used to represent the findings of cladistics in a visual way. A node is the place where a speciation event occurred. The larger clade is divided into a sister group + an outgrip which is less closely related to others in the cladogram. The base where other species branch out is called the root. The tips of the diagram = terminal branches. Cladograms are open for falsification so it changes.
A3.2.7 - Using cladograms
node= split in cladogram showing a hypothetical common ancestor, root = base of cladogram showing common ancestor of all clades, terminal branch = end of a branch representing most recently evolved of the organisms in the clade. Closer to the root, the further back in the past the cladogram represents + fewer derived characteristics the organism will have.
A3.2.8 - Cladistics and reclassification
Analysis of zones of DNA markers such as nuclear ribosomal internal transcribed spacer region has revealed that the old system was not monophyletic. Paraphyletic is species on seperate branches. Moving the branches of the tree of life + reclassifying a taxon in a new branch changes the species’ circumscription.
A3.2.9 - Three domains of life, not two
Top of classification hierarchy = 3 largest groupings for organisms = domains - Archaea, Eubacteria, Eukarya. Archaea = single-celled organisms distinct from bacteria. Extreme conditions archaea = extremophiles including thermophiles, methanophiles, halophiles. Eubacteria = domain which we find bacteria such as in yogurt to taste good helping the intestines work properly but are some that might give infection. Eukarya = all other life other than Archaea and Eubacteria from yeast cells to large organisms such as blue whales + trees. Separating archaea from other prokaryotes bacteria exists due to differences in the subunit of their ribosome (16s rRNA), metabolic reactions carried out by archaea that no bacteria can perform. Ways in which archaea read DNA to produce RNA + proteins for RNA, some physical features of archaea are diff. from bacteria such as types of molecules used to build their cell membrane + cell wall.
B1.1.1 - The variety of compounds containing carbon
Carbon-carbon covalent bond is two carbon atoms haring electrons. Hydrogen, oxygen, nitrogen, carbon, phosphorus, are all common w/ in molecules of living organisms. These are found in carbohydrates, proteins, lipids, and nucleic acids. They often form covalent bonds w/ carbon + each other. Covalent bonds for hydrogen = 1, Oxygen =2, Nitrogen = 3, Carbon = 4, Phosphorus = 5.
B1.1.2 and B1.1.3 - Condensation and hydrolysis
Macromolecules = smaller molecules 0 monomers. Digestion breaks down macromolecules as a result of chem. reactions called hydrolysis reactions. This breaks covalent bonds between monomers. Resulting monomers are then absorbed into the bloodstream + circulated to body cells. After entering the cells monomers are built up into macromolecules again. This involves forming covalent bonds in condensation reactions. The “R” notation indicates amino acids could be any of the 20 diff. possibilities. When a portion of the carboxyl group of 1 amino acid becomes oriented near the amine group of the other, stress is placed on the -OH of one amino acid + the H+ of the other. This results in the covalent bonds breaking + an -OH + H+is released but still contains a pair of electrons which form a new covalent bond. Whenever this occurs between 2 amino acids, the new bond = a peptide bond. The reaction is catalyzed by an enzyme. Foods are chemically digested in the alimentary canal - which are hydrolysing enzymes. In a hydrolysis reaction water is split.
B1.1.4 - Monosaccharides
Ribose + deoxyribose are monosaccharides + central components of the nucleotides RNA + DNA. Ribose = a pentose monosaccharide - meaning the carbon backbone is composed of five carbons. Chemical formula for this is …. Glucose is a hexose monosaccharide as its carbon backbone is composed of 6 carbons. Its chem. formula = …. Glucose is produced in photosynthesis + used in respiration. Glucose is used to make polysaccharides some for structural purposes, some for energy storage. Glucose is polar covalent and has: molecular stability, high solubility in water, easily transportable, yields a great deal of chemical energy.
B1.1.5 - Polysaccharides and energy storage
In amylose, carbon 1 is bonded to carbon 4 of the adjoining glucose. When hundreds of glucose molecule are bonded by 1-4 linkages its resulting molecule will be linear but in a helix shape. The 1-6 linkages are typical in amylopectin. Starch contains both of these. This has low solubility so can be easily stored. Glycogen is a polysaccharide made of glucose monomers.
B1.1.6 - Cellulose as a structural polysaccharide
Glucose beta + alpha are very similar but have reversed atoms on their right side. This affects the polymers formed by each side.
B1.1.7 - Conjugated carbon molecules
Glycoproteins on the surface of red blood cells determine a persons ABO blood type. Red blood cells can have two possible types of glycoproteins on their plasma membranes. The two proteins, A and B are called antigens. a person cannot receive an A or B blood antigen unless they have genetically inherited that glycoprotein.
B1.1.8 - Lipid solubility
Lipids are substances in living organisms that dissolve in non-polar solvents but are only sparingly soluble in aqueous solvents. Lipids include its, oils waxes and steroids. (non-polar due to the non-polar covalent bond)
B1.1.9 - Triglycerides and phospholipids
One glycerol molecule can link three fatty acid molecules or two fatty acid molecules and one phosphate group. Triglycerides contain one glycerol molecules and three fatty acid molecules.
B1.1.10 - Properties of fatty acids
Saturated fatty acids: single bond. High melting point due to this. Solid at room temperature. Monounsaturated fatty acids: one double bond. Lower melting point + oil at room temperature. Polyunsaturated fatty acids: more than one double bond. Low melting point + oil at room temperature.
B1.1.11 - Adipose tissue
Adipose tissue - cells that store fat in form of triglycerides. The properties of triglycerides make them suited to long-terms energy storage functions. These can be used as thermal insulators to body temperature and habitat.
B1.1.12 - Phospholipid bilayer
Amphipathic are molecules which have both hydrophobic and hydrophilic regions.
B2.1.1 and B2.1.2 - Membrane structure
Phospholipids and other lipids naturally form continuous sheet-like bilayers in water. The hydrophobic hydrocarbon chains that form the core of a membrane have low permeability to large molecules and hydrophilic particles, including ions and polar molecules, so membranes function as effective barriers between aqueous solutions.
B2.1.3 - Diffusion across cellular membranes
In diffusion, particles move from higher concentration to lower concentration. Oxygen is lower in concentration inside the cell compared to outside. Oxygen diffuses unto the cell as a result. CO2 diffuses in the opposite direction as it is produced in the cell. They move between the phospholipid molecules of the membrane so their diffusion occurs easily.
B2.1.4 - Membrane proteins
Membrane proteins have diverse structures, locations and functions. Integral proteins are embedded in one or both of the lipid layers of a membrane. Peripheral proteins are attached to one or other surface of the bilayer.
B2.1.5 and B2.1.6 - Membrane transport
Passive transport does not require cellular energy, active transport does. Passive transport: a substance moves from an area of high concentration to lower. Movement occurs along concentration gradient. Kinetic energy is the source. Active transport: substances move against the concentration gradient so energy expenditure occurs. Equilibrium is not reached but is reached in passive transport. Osmosis - passive transport. occurs across a partially permeable membrane. Hypertonic solution: higher concentration than hypotonic. Isotonic: equilibrium is achieved. Most cell membranes have aquaporins which allow water to pass through. Facilitated diffusion: involves carrier and channel proteins. Carrier proteins change shape to carry substances. Channel proteins: more pores which molecules of appropriate size and charge can move past.
B2.1.7 - Active transport and pump proteins
Active transport: requires work to be performed so energy is used (ATP) The sodium-potassium pump is an important example of active transport - uses ATP to move ions against a concentration gradient which is important in nerve cells - neurone so animals can respond to stimuli.
B2.1.8 - Membrane permeability
Size and charge decide how early a substance can move across a membrane. Facilitated diffusion an active transport allow selective permeability in membranes. Permeability by simple diffusion is not selective and depends on size and hydrophilic/hydrophobic properties of particles.
B2.1.9 - Glycoproteins and glycolipids
Glycolipids: when phospholipids have carbohydrate chains attached to them. Glycoproteins: cell membrane proteins which have chains of carbohydrates attached to them. These two are important for cell identification and cell adhesion. The characteristics of human blood types, A, B and O are the result of carbohydrate chains. Carb chains allows the body to decide which cells belong to it and which cells are from outside. (transplants) Rejection of the organ means the body’s immune system is attacking the foreign cells. Glycocalyx is a thin sugar layer made of carb chains attached to proteins which cover the cell. This coating allows for cell adhesion, cell to cell recognition, and reception of signalling chemicals.
B2.1.10 - The fluid mosaic model
Integral proteins: completely penetrate lipid bilayer, control the entry + removal of molecules from the cell. Peripheral proteins: supports membrane stability. Glycoproteins: composed of carb chains attached to peripheral proteins, play a role in recognition of like cells and are involved in immune responses. Cholesterol: helps to regulate membrane fluidity and is important for membrane stability.
B2.1.11 - Fatty acids and membrane fluidity
Unsaturated fatty acids in lipid bilayers have lower melting points, so membranes are fluid and therefore flexible at temperatures experiences by a cell. Saturated fatty acids have higher melting points and make membranes stronger at higher temperatures. (know the example of adaptions in membrane composition in relation to habitat)
B2.1.12 - Cholesterol and membrane fluidity
Cholesterol affects the plasma membrane fluidity =. They act to stabilize membranes at higher temperatures and maintain flexibility at lower temperatures. Plant cells have cell walls to stabilize the membrane so do not need cholesterol.
B2.1.13 - Bulk transport and membrane fluidity
Endocytosis allows macromolecules to enter the cell. Exocytosis: allows molecules to leave. Endyocytosis occurs when a portion of the plasma membrane is pinched off to enclose macromolecules or particles w/ in a vesicle of the cell. This allows a change in shape. Exocytosis: normally begins w/ the ribosomes of the rough ER + progresses through a series of steps: 1. Protein produced by the rough ER enters lumen. 2. Vesicle carrying the protein fuses w/ the cis side of the Golgi apparatus. 3. As the protein moves through the Golgi apparatus it is modified + exists on the trans face inside another vesicle. 4. Vesicle w/ the modified protein inside moves towards + fuses w/ the plasma membrane resulting in the secretion of the contents from the cell.
B4.2.1 - Species and ecosystems
Niche = unique role a species place in a community. Abiotic factors (non-living) affect the organisms habitat. These include sunlight, soil, pH + temp. Biotic factors (living) include relationships.
B4.2.2 - Obligate anaerobes, facultative anaerobes and obligate aerobes
Tolerance = how well a species reacts to the presence of something in its environment. Chem. transformation of nutrients into energy is aerobic respiration. nutrients to energy w/ no oxygen is anaerobic respiration. Obligate anaerobes = no tolerance to oxygen. Facultative anaerobes carry out both anaerobic + aerobic respiration. Obligate aerobes need oxygen to convert nutrients to energy. Hypoxia = oxygen reduced. Anoxia = absent oxygen.
B4.2.3 - Photosynthesis
The green pigment in organisms is chlorophyl used for photosynthesis. This is found in plants. Most organisms need sun to get energy. Autotrophs = organisms that make their food from inorganic substances such as photosynthesis. They can also be eaten by others so are producers.
B4.2.4 - Holozoic nutrition
Heterotrophs can’t make their own food. Holozoic nutrition = way of getting nutrients by ingesting the organisms. These are called consumers.
B4.2.5 - Mixotrophic nutrition
Organisms can be autotrophic + heterotrophic have mixotrophic nutrition. This is useful when sunlight is low. The genus Euglena is made up of protists that have photosynthetic pigments but also can ingest food so this is mixotrophic. Obligate mixotrophs need both systems to thrive. Facultative mixotrophs can survive on one system but use the other as a supplement.
B4.2.6 - Saprotrophic nutrition
Saprotrophs = live on non-living organic matter, secreting digestive enzymes + absorbing the products. Fungi + bacteria are saprotrophs called decomposers.
B4.2.7 - diversity of nutrition in archaea
Living thins categorized into 3 domains: Bacteria, Archaea + Eukarya. Archaea use photosynthesis, chemosynthesis, heterotrophic nutrition. Chemoautotroph = produces its own food using chem. reactions w/ no sunlight. Gets the energy through chemosynthesis.
B4.2.8 - The relationship between dentition and diet
Primates = Hominidae. Incisors = front teeth, canines to the side of incisors, premolars in the middle then molars in the back. Large incisors = mostly plant or fruit. Microwear = small abrasions on a tooth’s surface from chewing reveal the food they eat.
B4.2.9 - Adaptions of herbivores and plants
Aphids are insects which use stylets. Others use mandibles. Cows = ruminants - swallow grass before chewing. They then regurgitate it and chew more - chewing the cud. Herbivory - feed on plants. Thick bark/ thorns help plants defend themselves. Phytotoxins = plant poison which defends. Animals however evolve to neutralize the toxins. Colonies of microbes proliferate and can cope w/ the poison.
B4.2.10 - Adaptions of predators and prey
Behavioural adaptations - Teamwork - pack hinting Hughes the chance of defeating an animal. There is an established relationship. Known leader etc. Pursuit predators rely on speed to outrun its prey. Endurance also works which is persistence hunting. May behaviours are instinctive/ in DNA. Physical adaption include camouflage or aposematism - informs predators they are poisonous w/ unusual dramatic colours. Chem. reaction = venom/ poison.
B4.2.11 - Harvesting light
Trees use a canopy underneath is the understory where shorter trees are. Shrubs are shorter + frost floor is smaller non-woody plants. Lianas are vines that grown into the canopy to obtain more light. When seeds germinate they seek light and bend towards it. Liana however bends towards shade. Lianas are a direct competitor or trees (minerals sun + space) Epiphytes also take advantage of light through trees canopy or understory but these roots are not in the soil. Semi-epiphytes spend their life in a. tree w/ no roots till they push their stems downwards to reach the ground + grow roots. Herbaceous plants (herbs) do not produce a woody stem.
B4.2.12 - Ecological niches
Fundamental niche = potential niche it could inhabit. Realized niche = actual niche it inhabits. Diff. due to comp. w/ other species.
B4.2.13 - Competitive exclusion
Competitive exclusion = no 2 species can occupy the same niche. If they do coexist both populations will decrease. Interspecific comp. means 2 or more species. When these grow tog. they do significantly worse than alone.
B4.1.1 - What is a habitat?
Habitat - place where organisms live. When more than one species have similar requirements the place is a community if multiple lives. Habitats provide basic requirements - shelter, food water oxygen, light. Living organisms do not live in isolation but share habitats + impact another.
B4.1.2 - Adaption to the abiotic environment
Sand dune grass species lives on + creates sand dunes. Sea data = drought resistant + have a large shallow root system. W/ long roots helping reduce transpiration. they produce nodes + rhizomes near their base, above the sand line. When covered by blowing sand, the asexual growth shoots are stimulated + produce shoots above the sand. Sexual reproduction is accomplished w/ production of seed heads resembling a true oat plant. Mangrove tree species - grows along saltwater. The prop roots extend above the water line. there lots above the water line also absorb air. The air oxygenates the root tissues which are below the water line buried in mud. The roots below the water line filter salt out of the water so the tree has fresh water. Red ,mangroves adapted to changing water levels so the tangles root growth under the trees provides a protective habitat for many marine animals. Red mangroves produce a fruit containing a seed that germinates + begins to grow before falling from the parent plant. The young plant is called a propagule - this eventually falls from the tree + floats in the water below. After absorbing the water the propagule orientates itself in shallow water w/ its roots downwards + begins early root growth. A shoot w/ early leaves grows from the opp. end. This is an adaption for plant dispersal in a marine environment.
B4.1.3 - Abiotic variables
Any abiotic factor (non-living) can act as a limiting factor is it is outside the tolerance zone of an organism. Some organisms developed special adaptions that extend their tolerance range w/ in their habitat. Many catfish can take in oxygen through skin - live in oxygen-poor habitats.
B4.1.4 - Limiting factors
Limiting factor (abiotic/biotic) limits a population size. It limits the abundance of a species.
B4.1.5 - Coral reef formation
Corals = a symbiotic relationship between coral polyps + microscopic algae (zooxanthellae). Both organisms require suitable growth conditions. Small size of the ocean SA populated by coral reefs is an indication that the combo. of all the right abiotic factors for these symbiotic species is rare. Table on 331.
B4.1.6 - Terrestrial biomes
A biome is a large geographical area that contains communities + plants adapted to living in that environment. Biomes are often dominant vegetation type that is found w/in the biome. Biomes are created by varying conditions of precipitation + temp. can be plotted on a graph.
B4.1.7 - Biomes, ecosystems and communities
Plants + animals found in similar biomes that are geographically separated will have diff. genetic backgrounds.Morphology + physiology will be similar but organisms in a community will have little genetic similarity. Convergent evolution is the reason for this. Similar species that live w/in the same ecosystem are often genetically related as often they are a result of adaptive radiation. Table on 335.
B4.1.8 - hot deserts and tropical rainforests
The saguaro cactus has thick waxy skin as waterproof + covered in bristles as a defence. Also a long taproot that sends down to retrieve deep water + massive shallow root system to absorb rainwater. The fennec fox has vascular ears that help dissipate heat. Large helps help locate small prey animals. The kapok tree - strong foundation from buttress roots that extend above ground. Poison-dart frogs - developed highly toxic chemicals in their skin as a result of their diet of poisonous insects. Evolved to have bright colours + body patterns to warn predators.
B3.3.1
B3.3.2
B3.3.3 - Antagonistic muscle pairs and titin
Muscles use connective tissues - tendons to attach 2 bones. One bone is an immovable anchor (origin) while the other (insertion) moves as a result of the muscle contraction. Two muscles accomplish opp. movements are antagonistic to each other. Muscles use a force to help w/ relocation as a result of the spring-like action of a protein called titin - an immense protein that has multiple folds allowing it to act like a spring. When sarbomers shorten during a contraction the 2 sides of each sarcomere move towards the centre creating a spring-like tension in titan that is released when the muscle relaxes. This allows each sarcomere of the muscle to undergo a contraction again. titan also holds myosin fibres in place in the sarcomere + prevents muscle fibres overstretching.
B3.3.4 - Motor units
Nervous sytem controls skeletal muscle contraction. Every movement requires many electrical impulses in the brain + terminating at synapses called neuromuscular junctions. These junctions are a type of synapse where a chem. message sends into the muscle tissue - stimulating a contraction. Neurons that carry these messages are called motor neurons. Each motor neuron has a set number of muscle fibres that controls to - motor unit. If a low intensity contraction is needed a low number of motor units is activated by the brain.
B3.3.5 - skeletons as levers and anchor points
Arthropods have an exoskeleton made of chitin. Skeleton is on the outside + has a hollow skeleton. Many individual bones of skeletons act as levers. A lever is a rod able to rotate about a fixed point known as a fulcrum (joint).
B3.3.6 - synovial joints
Synovial joints occur where 2 bones need to move against each other + notable for wide range of motions that they allow. (elbow, knee, shoulder, hips) Head of a demur forms a ball that fits into. rounded socket in the pelvis bone - ball-and-socket joint. Entire joint is encased by a membrane that contains a lubricant - synovial fluid. Hip joint is encircled by tough fibrous ligaments that hold bones in place but allow movement. Numerous muscles exist controlling movements of the hip joint each w/ tendons that connect the bones. Table on 316.
B3.3.7 - Range of motion
Goniometers measure a range of motion of a joint.
B3.3.8 - antagonistic muscle action
External intercostal muscles are the first muscles seen looking from the outside. Beneath are the internal intercostal muscles. When external intercostal muscles contract, the rib cage is pulled upwards + out. This occurs during inspiration. Antagonistic internal intercostal muscles move the ribcage down + inwards during expiration. Movement of the ribcage + diff. orientation of the muscle fibres permit stretching of the muscle layer that is not being contracted. When external intercostal muscles contract the expansion of the ribacage results in stretching of the internal intercostal muscles. this stretches the titan fibres in each sarcomere of the muscle layer creating potential energy that can be used for the next contraction of internal intercostal muscles.
B3.3.9 - The need for locomotion
Most animals rely on location for a variety of reasons - food, finding a mate, escaping predators/migrating. Table on 319.
B3.3.10 - Swimming adaptions
Dolphins whales +seals all descended from ancestral species that once lived on land. Their internal anatomy is adapted to a marina environment but still has many similarities w/ land ancestors. They have a streamlines body, have lost all body hair, have a tail adapted to form a fluke, have lost rear legs, have front limns adapted to become flippers, have a airway blowhole, can seal the blowhole between breaths so no water enters, can stay underwater for minutes w/ no breathing, have retained mammalian characteristics - endothermic, producing milk, advanced two-sided circulatory system, long-term parental care of their young.
B3.2.1 - Capillaries and chemical exchange
Capillaries receive their blood from smallest arteries - arterioles. W/in body tissues arteriole branches into a capillary bed - network of capillaries that receive blood from same arteriole. Single capillary bed drains its blood into a venule (smaller vein) Blood lines up in a single file due to the lumen od each capilarru is only large enough to hold one cell at a time. Each capillary is a small tune composed of a single-cell thickness of inner tissue + a single-cell thickness of outer tissue. Both layers are very permeable. Total SA is very high. Metabolically active tissues are enriched w/ capillary beads known as highly vascular tissue. Some are more permeable so are fenestrated that allow large molecules to emit or enter. Capillaries: small inside diameter, thin walled, permeable, large SA, have fenestrations (in some)
B3.2.2 - Arteries and veins
Arteries receive blood from the heart + takes it to a capillary bed, veins receives blood from a capillary bed + takes it back to the heart. Arteries go through high pressure so are lines w/ a thick layer of smooth muscle + elastic fibres. The lumen is smaller than veins.
B3.2.3 - Adaptions of arteries
Arteries transport high pressure blood away from the heart. When the heart contracts a surge of blood enters an artery + its branches. Artery has a thick layer of smooth muscles controlled by the autonomic nervous system which controls those functions in the body that are not conscious. Each wall contains proteins elastin + collagen. The muscular + elastic tissues permit arteries to withstand high pressure of each blood surge. When blood is pumped into an artery, the elastin + collagen fibres are stretched + allow the blood vessel to accommodate the increased pressure. They then recoil propelling blood forwards w/ in the artery. So the arteries maintain a high pressure between pump cycles of the heart.
B3.2.4 - Measuring pulse rate
Pulse rate is a measurement of the number of times your heart beats a minute. The carotid artery + radial artery can be touched to feel pulse rate.
B3.2.5 - Adaptions of veins
Blood loses a lot of pressure + velocity in capillary beds so veins have thin walls + thin diameter. the unidirectional flow of slow-moving blood is aided by internal valves that prevent back glow of blood. Veins are easily compressed by surrounding muscles - activity is needed for this.
B3.2.6
B3.2.7 - Water transport from roots to leaves
Plant relies on transpiration to bring water + dissolved merls up from roots. Water is located in the air spaces created by the spongy mesophyll layer of the leaf. Loss of water by transpiration caused water to be pulled through the cell wall of nearby xylem tissue by capillary action/ This creates tension at the upper end of each xylem tube. This result sin movement of water up the xylem + entire column moves up due to cohesion. Upwards movement of water w/ dissolved minerals = cohesion-tension theory.
B3.2.8 - Adaptions of xylem vessels
B3.2.9
B3.2.10
B3.2.11
B3.2.12
B3.2.13
B3.2.14
B3.2.15 - The mammalian heart
right side of the heart sends blood to + from the lung capillaries in a route - pulmonary circulation. The left side of the heart sends blood to + from tissues called systemic circulation. Advantage = both lung + blood capillaries can receive blood from arteries + arterioles. this allows pressure filtration to occur in all capillaries. Cardiac muscle - highly vascular tissue making up the heart muscle, pacemaker - sinoatrial node is an area of specialized cells in the right atrium generating electrical impulses to start each heartbeat. Atria - thin muscular chambers that receive low pressure blood from capillaries of the lungs. Sends blood to the ventricles. Ventricles - thick chambers that pump blood under pressure to lungs/body. Atrioventricular valves - located between the atria + ventricles that close each heart cycle to prevent any back flow of blood to atria. Semilunar valves - close after surge of blood into pulmonary artery to prevent back flow into ventricles. Septum - wall of tissue separating right and left of the heart. Coronary vessels - provide oxygenated blood to heart.
B3.2.16 - The cardiac cycle
Cardiac cycle leads to one heartbeat. A systole is when the chamber of the heart contracts causing an increase in pressure on the blood w/ in the chamber + blood leaves the chamber through any opening. The diastole is when a chamber is not undergoing a systole the cardiac muscle relaxes. The SA node is a croup of cardiac cells in the right atrium. It provides an electrical stimulation to regulate the contractions. If the myogenic (resting) is 72 beats per minute, the SA node is generating impulses every 0.8 seconds. Action potentials from SA node spread out almost instantly + results in the atria undergoing systole. the SA node potential reaches the atrioventricular node located in the right atrium in the septum between the right + left atria. An electrocardiogram is a graph w/ electrical activity from the SA + AV.
B3.2.17
B3.2.18
B3.1.1 - The exchange of gases between organisms and their environment
As organisms increase in size it becomes more difficult to exchange oxygen + CO2 through the plasma membrane . With the surface area-to-volume ratios decreasing w/ increasing size, the distance from the centre of an organism to its exterior increases. These organisms have evolved adaptions to exchange respiratory gases. The volume of an organism shows its metabolic need to exchange respiratory gases.
B3.1.2 - Gas exchange surfaces
Gas exchange surfaces characterized by: being thin, moist, large SA, permeable to respiratory gases. A salamander has six gills for gas exchange.
B3.1.3 - Concentration gradients at exchange surfaces in animals
As oxygen + CO2 are exchanged by diffusion, concentration gradients must be maintained for oxygen to diffuse into the blood + CO2 out. When blood is circulated to the gills, it has recently been w/ in capillaries of tissues. Body cells are constantly respiring, utilizing oxygen then producing CO2. The blood that leaves body tissues contains a higher concentration of CO2 + lower oxygen compared to levels before the blood reached the tissues. The blood is then transported to the gill tissue + exchanges occur again. Diffusion gradients explain the gas diffusion taking place in animals w/ lungs. @ events occur to keep concentration gradients in place - water must be continuously passed over gills or refreshed in lungs, must be continuous blood flow to dense network of blood vessels in body + gills/lungs.
