chapter 8
List the structures that protect the central nervous system
List the structures that protect the central nervous system.
List the ways that a pathogen can pass from an infected person to someone else.
Transfer by contact, ingestion, transfer of body fluids, infection by droplets, airborne transmission, transmission by vectors
Will the shorter or longer lengths of DNA travel the greatest distance during electrophoresis? Explain your answer.
The shorter lengths will travel further. They encounter less resistance from the agarose gel.
Define ‘pentadactyl’ and ‘opposable’.
Pentadactyl refers to having five digits on each limb. Opposable means the first digit can be moved in such a way that it can touch each of the other digits.
Explain why variation is crucial for natural selection.
Variation is crucial because it provides different physical characteristics for the selective agent to act on. If there was no variation in a population, the selective agent could act to remove all members of the species.
What causes type 1 diabetes?
Type 1 diabetes is an autoimmune disease where the person’s immune system destroys beta cells in the Islets of Langerhans in the pancreas.
Which cells release heparin and histamine following tissue damage?
mast cells
Define ‘genome’.
double points for describing how sequencing the genome can be used to provide evidence for evolution.
The complete set of DNA in each cell of an organism is called the genome.
Sequencing the genome and comparing sequences of human genome with the genome of other organisms, researchers are able to identify regions of similarity and difference. This provides evidence for evolution because the more similar the sequences, the organisms are more closely related.
An unknown species is discovered. It has five fingers with claws, an opposable thumb and a small cerebrum that has limited convolutions. Would the species be classified as being a member of the family Hominidae? Explain your answer.
No. This species is unlikely to be a member of Hominidae due to the presence of claws and a small brain with limited convolutions.
Explain why only germline mutations are passed on to the next generation.
Germline mutations are mutations that have occurred in the gametes. In these instances, the individual cells are rarely affected, but all their gametes will contain the mutated DNA.
List three ways that gene therapy could possibly correct faulty genes
Describe the role of cilia in the external defence mechanisms.
Cilia are tiny hair-like projections from cells that are capable of a beating motion. The beating motion moves mucus containing trapped particles and micro-organisms towards the throat where it may be coughed up or swallowed.
Suggest what would happen if the temperature were too high during the annealing step of PCR
Primers would not be able to attach, the lower temperature allows hydrogen bonds to form between the DNA strands and the primers.
Define ‘carrying angle’ and explain why it allows a striding gait.
The carrying angle is generated by the wide apart hip bones and the convergence of the femurs towards the knees. This arrangement of the femurs forms an angle to the vertical which is called the carrying angle. It allows striding gait as the weight distribution remains close to the central axis of the body when walking. The body is able to be rotated about the lower leg and foot, so each footstep follows a more-or-less straight line.
Define ‘gene flow’ and how migration facilitates it
double points to list 4 barriers of gene flow
Gene flow is the movement of genetic material from one population to another, Migration is when individuals move between populations and enabling gene flow. The people entering or exiting the population move their genes with them.
Geographical barriers include oceans, mountain ranges, large lake systems, deserts and expansive ice sheets. Sociocultural barriers include economic status, educational background and social position.
What are stem cells, and why are they suitable for cell replacement therapy?
What are stem cells, and why are they suitable for cell replacement therapy?
Why is the secondary response quicker and longer lasting than the primary response
Second or subsequent exposures to the same antigen results in a quicker and longer lasting response due to the action of memory cells. The plasma cells are able to form very quickly, with antibody levels in the blood plasma rising rapidly to a higher level that lasts longer.
Describe how endogenous retroviruses are used as evidence for evolution.
Endogenous retroviruses appear in the non-coding sections of DNA. As they are inherited, they will appear in the same location of DNA in different species that share a common ancestor. The more aligned the location of the ERVs are, the more similar the two species are
Explain why bipedalism would have allowed ‘survival of the fittest’ during natural selection
Bipedalism is a more efficient way of walking larger distances. It frees up the hands for carrying infants, reaching for food or making and holding stone tools. Bipedalism also allowed for better thermoregulation, a necessity as the forest was receding into grasslands. The ability to be bipedal would have been an advantage in the changing climate and changing environment about 8 million years ago. As such the individuals with the characteristics would have survived, reproduced, and passed the characteristics on to their offspring.
Explain why genetic drift is unlikely to have a significant effect on the allele frequency of a large population.
Genetic drift occurs in large populations but is more pronounced in small populations because they have less variation and a lower ability to respond favourable to changing conditions. Small populations will change quickly in fewer generations. Genetic drift does not take into account allele benefit or harm; therefore, in a small population, beneficial alleles may be lost, or a harmful allele may become fixed purely by chance. This would not occur in a larger population.
how many skin cells are shed every minute
30,000 to 40,000
Explain how it is possible to introduce a virus or bacteria in a vaccine without producing the associated disease.
A vaccine may contain either a dead pathogen, a sub-unit of the protein coat of a virus, or a pathogen that has been attenuated. These vaccine types will not result in the person getting the disease or the symptoms associated with the disease. They will produce an immune response and memory cells for the person being vaccinated.
pick out the lie
1. Earwax is actually a type of sweat.
2. The strongest muscle (by size) is the jaw
3. Your stomach gets a new lining every 7-9 days
3. its actually every 3-4 days
Explain why doctors are reluctant to amputate the big toe.
The big toe has lost its opposability as it has become a weight-bearing appendage. When striding, the whole weight of the body is propelled by the big toe. Doctors would be reluctant to amputate the big toe because the person’s gait would be affected.
Is mutation, natural selection or genetic drift the most important process in speciation? Justify your answer.
Mutation is the most important. Mutation provides a source of variation, without variation natural selection and genetic drift will have no differing effects leading to speciation.