Chapters 19 & 20 Work

Derek Lee

Mr. Hillegas

Ap Biology

Chapters 19 & 20 Work

II.

1.      Sympatric speciation is a speciation model that occurs inside the home range of a species in the absence of a physical barrier by way of polyploidy. This occurs when individuals inherit three or more sets of chromosomes when a somatic cell fails to divide mitotically after its DNA, is duplicated, or nondisjunction occurs at meiosis and results in an unreduced chromosomes number of gametes,  as a result of the incorrect separation by microtubules.

2.      Endosymbiosis & Atmospheric Gases- Endosymbiotic relationships began millions of years ago when certain prokaryotic cells had adapted to the concentration of free oxygen atmospheric concentration of gases and were already engaged in aerobic respiration. The ancestors of eukaryotic cells preyed upon some aerobic bacteria that were parasitized by others, thus beginning endosymbiotic interactions.

3.      Adaptive radiation & Character Displacement- Resource partitioning occurs when at least 2 species overlap, in which the specific individuals that are able to pursue these resources in slightly different ways (partitions), in order to minimize competition, will be the most successful, and those traits will be selected for character displacement. This occurrence creates adaptive zones which are necessary for adaptive radiation, or the burst of divergences from a single lineage that leads to many new species. I.E. Hawaiian honeycreepers.

4.      Proto-cells & Uracil- rRNA components of ribosomes catalyzes protein synthesis whose structure and function of ribosomes have been conserved over time and whose catalytic behavior probably evolved early in Earth history. Coenzymes and metal ions assist most enzymes and certain coenzymes are structurally identical with RNA subunits. Two of RNA’s building blocks cytosine and uracil- proteins may have evolved into the earliest form of proto-cells.

III.

1.      Prezygotic Mechanisms: Stop cross-pollination or cross-breeding, the formation of gametes, or fertilization.

- Mechanical isolation: Individuals can’t mate or pollinate because of physical incompatibilities

-          Temporal Isolation: Individuals of different species reproduce at different times.

-          Behavioral Isolation: Individuals of different species ignore or don’t get the required cues for sex.

-          Ecological isolation: Individuals of different species live in different places and never meet up.

Postzygotic mechanisms: Kill hybrids or make them weak or infertile.

-          Hybrid inviability: Hybrid embryos die early or the new individuals die before they can reproduce.

-          Hybrid sterility: Hybrid individuals can’t make functional gametes.

2. The gradual model of speciation says that species originate by slight morphological changes over long time spans. It shows gradual morphological change as with minute changes In fossil sequences over time. Punctual equilibrium offers a different explanation for patterns of speciation, saying morphological changes are said to evolve in a relatively brief geologic period, within the tens to hundreds of thousand of years when populations are starting to diverge.  This may occur through directional selection, genetic drift, the founder effect, bottlenecks, or some combination of them which favor rapid speciation.

3.   Stanley Miller was the first to test the hypothesis that the simple compounds that now serve as the building blocks of life can form by chemical processes. He put water, methane, hydrogen, and ammonia in a reaction chamber. He kept circulating the mixture and zapping it with sparks to simulate lightning. In less than a week, amino acids and other small organic compounds had formed in the chemical brew.

4. Membranes – Mitochondria have their own cell membranes, just like a prokaryotic cell.

- DNA – Each mitochondrion has its own circular DNA genome, but much smaller. This DNA is passed from a mitochondrion to its offspring and is separate from the host cell’s genome in the nucleus.

Reproduction- Mitochondria multiply by pinching in half – the same process used by bacteria. Every new mitochondrion must be produced from a parent mitochondrion in this way; if a cell’s mitochondria are removed, it can’t build new ones without a “parent” mitochondrion.

Mitochondria resemble tiny bacteria making their livings inside eukaryotic cells. Such is common to other cellular organelles including chloroplasts or tiny factories within plant cells that help convert energy form sunlight into sugars. These organelles have become completely dependent on their host cells. As such these are all evident from endosymbiosis.

5. On Note Card

Chapter 17 & 18 Work

Derek Lee

Ap Biology

Period 4

Chapters 17 & 18 Work

II.

1.      Prophase I, Allele Frequency- Allele frequencies are those relative abundance of alleles of a give gene among all individuals of a population that can start from a theoretical reference point, genetic equilibrium, when a population is not evolving with respect to that locus. However, this genetic equilibrium and thus allele frequency can be thrown off by natural selection, genetic drift, natural selection, or the wild card of mutations; some of which arise during prophase I of meiosis due to crossing over during prophase I, independent assortment, etc.

2.      Natural Selection, analogous structures- Analogous structures are those with dissimilar body parts that have become similar in structure, function, or both in lineages that are not closely related but were subjected to similar pressures. Regardless, such creatures evolved over time via mutations that occur in populations in response to the environment, in this case environmental pressures. These evolutions may result from natural selection and the passing of favorable traits based on environmental pressures.

3.      Bottleneck and Gene pool- Bottleneck is a drastic reduction in population size brought about by severe pressure. A gene pool is the pool of genetic resources for a population. If large numbers of a population are wiped out, this decreases the gene pool and thus genetic variation.

4.      Balance polymorphism and search image-Balanced selection occurs when two or more alleles of a gene are being maintained at relatively high frequencies in the population, their persistence is balanced polymorphism. Such is seen with certain genetic disorders such as sickle-cell anemia. Search images may how this distribution of disease over its density with i.e. a country.

III.

1.      - Observation: Natural populations have an inherent reproductive capacity to increase in size over time.

-Observation: No population can indefinitely grow in size, because its individuals will run out of resources-food, space, etc.

-Inference: Individuals will end of competing for dwindling resources.

-Observation: Individuals share a pool of heritable information about traits, encoded in genes.

-Observation: Variations in traits start with alleles, slightly different molecular forms of genes that arise through mutations

-Inferences: Forms of traits are more suited for the individual to survive. These alleles for adaptive forms become more frequent and lead to increased fitness- an increase in adaptation to the environment as measured by the genetic contribution to future generations.

-Conclusions: Natural selection is the outcome of differences in reproduction among individuals of a population that vary in shared traits.

2. –Origin of Earth’s crust, first atmosphere, first seas. Chemical, molecular evolution leads to origin of life from proto-cells to anaerobic prokaryotic cells

- Origin of photosynthetic prokaryotic cells.

-Oxygen accumulates in atmosphere. Origin of aerobic metabolism. Origin of eukaryotic cells. Divergences of lead to eukaryotic cells, then protists, fungi, plants, and animals.

-Major crustal movements. Ice ages. Mass extinction of many marine species. Vast swamps form. Origin of vascular plants. Adaptive radiation of fishes continues. Origin of amphibians.

-Recurring ice ages. On land, adaptive radiations of insects, amphibians. Spore-bearing plants dominate; cone-bearing gymnosperms present. Origin of reptiles.

-Adaptive radiations of marine invertebrates, fishes, dinosaurs, Gymnosperms dominate land plants. Origin of mammals.

-Early Cretaceous Mesozoic and Cenozoic tertiary – Major crustal movements, collisions, mountain building, Tropics, subtropics extended pole ward. When climate cools, dry woodlands, grasslands emerge. Adaptive radiations of flowering plants, insects and mammals, and origin of angiosperms.

3. Evolution does not happen on the individual level, but happens in populations over time. Evolution is drive by the environment, which favor certain traits. Thus variation is absolutely necessary for evolution to take place. The environment doesn’t create the adaptations, it simply favors some and not others. Variations are differences in traits, which are determined by genes. More specifically, the “variations” we are speaking of are variations in the frequency of alleles in a population. An individual may not just evolve: i.e. grow longer arms merely out of necessity but rather through populations whose environment favors their traits/adaptations which help them survive and is thus passed on from generation to generation (speciation).

4. Gene mutations- changes in the sequence of DNA bases within a gene. Frame shift and point/substitution mutations.

Crossing over at meiosis I (puts novel combinations of alleles in chromosomes)- producing genetic variation some of which may produce a mutation proving beneficial leading to genetic variation.

-Independent assortment at meiosis I (puts mixes of maternal and paternal chromosomes in gametes) Chromosomes are inherited independently of one another.

-Fertilization (combines alleles from two parents)- for sexually reproducing species, the population of individuals that are interbreeding, reproductively isolated from other species producing fertile offspring. Have traits which show qualitative and quantitative differences for a specified trait.

-Change in chromosome number or structure (loss, duplication, or repositioning of genes)- thought often leads to severe mental or physical impairments results from mutation.

5. p2 (AA) + 2pq (Aa) + q2 (aa) = 1.0

P and q are the frequencies of alleles A and q. It defines the frequency of a dominant and a recessive allele for a gene that controls a particular trait in a population. The frequencies of A and a must add up to 1.0.

Ap Biology Chapters 15, 16, and 21 Work

Derek Lee

Mr. Hillegas

Ap Biology

13 March 2011

Chapter 15, 16, and 21 Work

II. Connections

1.      Lysogenic and Binary Fission- During a lysogenic pathway, a virus does not kill its host outright, but rather a viral enzyme cleaves the host’s chromosomal DNA, then integrates the viral genes into its base sequence. The infected cell eventually divides, and replicates its DNA, including all of the foreign genes in the recombinant molecule, i.e. miniature time bombs are passed on to its descendents. These infected cells, viruses, may infect other bacterium, in which the virus will be passed on through the bacteria cells via binary fission, the replication of a prokaryotic cell.

2.      Conjugation and Bacterial transformation- Conjugation is a process that involves the transfer of genetic information from one bacterial cell to another, and requires physical contact between the two bacteria involved via a protein tube called an F or sex pilus, which is also the conduit for the transfer of genetic material. During transformation, bacteria will pick up DNA from their environment from a number of sources, most notably the remnants of DNA from dead bacterial cells. One way for this genetic material to be “picked” up is through conjugation – the physical touch and sex pilus.

3.      Plasmid and retrovirus- Retroviruses carry an enzyme causes a process known as reverse transcription in the DNA to occur. It fools the DNA to copy it rather than RNA leading to the creation of more retroviruses resulting in cells that carry the viruses for life and only further duplicate. Plasmids are small, self-replicating circles of DNA which show how such viruses can be passed on through conjugation and thus physical touch.

4.      Operator and hydrolysis- hydrolysis is a chemical reaction or process wherein a water molecule and a reactant exchange functional groups resulting in two end products. It is the process of splitting a compound into fragments with the addition of water, breaking down polymers into simpler units, i.e. starch into glucose. Operations are segments of DNA where the repressor binds to, thereby preventing the transcription of certain genes; both of which stop the chemical processes leading to the replication of DNA.

5.      Okazaki Fragments and restriction enzymes – Okazaki fragments are formed when the 5’ to 3’ end of the DNA adds grows from the top to bottom resulting in unconnected or Okazaki fragments. Restriction enzymes catalyze the cleave of DNA at restriction sites, producing small fragments for gene splicing, aiding the connection between the fragments.

III. Few Essentials

1.      At control before transcription the access to genes is under control. Where a DNA molecule is wound up tightly, polymerases cannot access genes. Acetylation can make histones loosen their grip and or a maternal or paternal allele at any locus in a diploid cell may become methylated which can block the gene’s influence on a trait. Such controls also affect how a gene will be transcribed, some gene sequences can be rearranged or multipled.

Controls of transcript processing influences mRNA transcript processing. Such examples include the nuclear envelope which helps control when mRNA transcript reaches a ribosome. The transcript can not pass through a nuclear pore complex unless proteins become attached to it. A base sequence in the untranslated end of mRNA is like a zip code.  Controls “read” the code and attach proteins to it. During translation certain controls work on initiation factors and ribosome components. Others work through mRNA transcript stability. Controls after translation is controlled by new enzymes and other proteins. For example, Y-box proteins become activated only when enzymes attach a phosphate group to them. Other controls activate, inhibit, and stabilize diverse molecules that take part in protein synthesis. Allosteric control of tryptophan synthesis is a case in point.

2.      Note card~

3.      Gel electrophoresis separates an individual’s DNA fragments from one another according to size. AN electric current repels a mixture of the negatively-charged DNA fragments thru microscopic pores in the gel from the negative to positive electrode. Upon completion, the separated fragments of DNA can be visualized as a ladder of small bands in the gel by staining with methylene blue dye solution. It is a procedure for separating a mixture of molecules through a stationary material (gel) in an electrical field.

4.      Eukaryotic cells divide through mitosis whereas prokaryotic cells divide through prokaryotic (binary) fission. Prokaryotic fission starts when a cell replicates its DNA. The parent molecule and the copy are both anchored to the plasma membrane at adjacent sites. Meanwhile, the cell is synthesizing proteins and lipids, which become added to the plasma membrane between the two attachment sites. The additions make the membrane grow, which moves the molecules of DNA apart. New wall material is deposited onto the growing membrane, and growth continues on through  the cell midsection. It cuts the cytoplasm in two, the result being two genetically equivalent daughter cells.

5.      The lytic cycle is one of two cyclecs of viral reproduction, which is usually considered as the main method of viral reproduction because it ends in lysis of the infected cell releasing the progeny viruses that will in turn spread and infect other cells. A virus undergoes lytic and lysogenic cycles to reproduce. The lytic cycle vs. lysogenic cycle takes place when the virus gets itself attached to the outcer cell wall of a bacterium. Then it releases enzymes to weaken the cell wall of the bacteria. Then, virus injects its genetic material, that is, either double stranded DNA or single stranded RNA, depending o the virus. The lytic cycle causes the host bacterium to undergo cell lysis or cell destruction whereas the lysogenic cycle does not cause the host to lysis. The lytic cycle can lead to the production of 100-200 progeny phages vs lysogenic in which the DNA of the phage gets integrated into the bacterial chromosome and no progeny are produced mostly. The lytic cycle can not be converted into the lysogenic cycle but the lysogenic cycle can be converted into the lytic cycle when the host cell is exposed to chemical or physical agents.

Ap Biology Chapters 13 & 14 Work

Derek Lee

Mr. Hillegas

Ap Biology

7 March 2011

Chapters 13 & 14 Work

II. Connections

1.      5’ & electronegativity- 5’ refers to DNA polymerase enzymes joining the phosphate group at 5’ carbon. In this sense bonds between atoms are based on charges in which the electronegativity between two types of atoms determines what types of bonds they will form. For example prior to this step 5’, helicases must unzip and break off weak hydrogen bonds.

2.      Start codon & incomplete dominance – Start codons or chain initation codons, AUG or GUG, signal the initiation of translation and the first amino acid in a polypeptide chain. Genes code for the proteins which express traits. In the case of codominance, two phenotypes are expressed equally, in which the proteins must be both signaled for translation and thus expression.

3.      Semiconservative & barr body- Semiconservative replication is the normal process of DNA synthesis, in which the two original strands of molecule separate, and each acts as a template on which a new complementary strand is laid down. In females, on of these two strands of chromosomes, DNA, through process of x-inactivation will become unread and thus a bar body. This prevents females from having such a difference of DNA in comparison to males.

4.      RNA Polymerase & nucleolous- RNA polymerase is a catalyzes the synthesis of a complementary strade of RNA from a DNA template. At the nucleolous RNA, specifically mRNA help translate the words in protein-building messages- they are the translators which give words that orginiated in the DNA their meaning. The nucleolous uses this information to make proteins.

5.      DNA Polymerase & Glycosidic linkage- DNA polymerase refers to anyi of various enzymes that function in the replication and repair of DNA by catalyzing the linking dATP, dCTP, dGTP, and dTTP, in a specific order using single-straded DNA as a template. These bonds it makes are sugar/ glycosidic linkages.

6.      Helicase & G2 Karyotype- A G2 Karyotype shows the chromosomes like a normal karyotype after Synthesis phase, meaning it will show the duplicated or double the normal amount of chromosomes. Helicase, or enzymes will unwind the deoxyribonucleic acid double helix at a replication fork in the process of DNA replication to form two new strands of DNA.

III. Essentials

1.      2 DNA strands are anti parallel, yet DNA polymerase can only synthesize new DNA in the 5’ to 3’ direction. This poses special problems for replicating double-stranded DNA. To begin replication, unwinding enzymes called DNA helicases cause two parent DNA strands to unwind and separate from on another at the origin of replication. Helix destabilizing proteins bind to the single-stranded regions so the two strands do not rejoin. Enzymes called topoisimerases produce breaks in the DNA and then rejoin them in order to relieve the stress in the helical molecule during replication. As the strands continue to unwind and separate in both directions around the entire DNA molecule, new complementary strands are produced by the hydrogen bonding of free DNA nucleotides with those on each parent strand.

2.      DNA is double stranded, contains deoxyribose sugar, and contains thymine base.

RNA is single stranded, has ribose sugar, and has a uracil base.

3.      tRNA – information adapter molecule. IT is the direct interface between amino-acid sequences of a protein and the information in DNA.

mRNA- A copy of the information carried by a gene on the DNA. It functions to move the information contained in DNA to the translation machinery.

rRNA- A component of ribosomes, the protein synthetic factories in the cell.

4.      A.- In transcription, only one part of one DNA strand, not the whole molecule, is unwound and used as the template strand.

-The enzyme RNA polymerase, not DNA polymerase, adds ribonucleotides one at a time to the end of a growing strand of RNA.

-Each DNA protein-coding region has its own start and stop signal.

-A promoter is the start signal, a base sequence in DNA to which RNA polymerases bind and prepare for transcription.

-Using the gene’s base sequence as the template for covalently bonding free ribonucleotides together in a complementary sequence, the end result is a new GNA released as a free transcript.

B. RNA Splicing – process which removes intros and joins exons in a primary transcript. -An intro usually contains a clear signal for splicing.

-In some cases, a splicing signal may be masked by a regulatory protein, resulting in alternative splicing.

-In rare cases, a pre-mRNA may contain several ambiguous splicing signals, resulting in a few alternatively spliced mRNAs.

-It is the process by which base pairs that interrupt the continuity of genetic information in deoxyribonucleic acid are removed from the precursors of messenger ribonucleic acid.

C. Translation – Is the process of converting the mRNA codon sequences into an animo acid polypeptide chain.

-Each tRNA has a molecular “hook,” an attachment site for an amino acid. It has an anticodon, a ribonucleotide base triplet that can base-pair with a complementary codon in an mRNA transcript.

-This process has 3 steps beginning with initiation, or when a ribosome attaches to the mRNA and starts to code at the FMet codon – AUG, GUG, or UUG.

-Second, in elongation, tRNA brings the corresponding amino acid to each codon as the ribosome moves down the mRNA strand.

-And last, termination, or the reading of the final mRNA codon – the STOP codon – which ends the synthesis of the peptide chain and releases it.

Chapter 11 & 12 Work - Genetics

Derek Lee

Mr. Hillegas

Ap Biology

14 February 2011

Chapter 11 & 12 Work

II. Connections

a.       Gene locus & disulfide bridge- The gene locus is the location for a specific gene on a chromosome which might code for making a specific protein. If the protein undergoes tertiary or proceeds to quaternary folding, further folding into a specification 3D conformation takes place as a result of disulfide bridges, which form between sulfur atoms in neighboring cysteine amino acids.

b.      Nondisjunction & 9-triplet pattern- MTOC’s (Basal Bodies and centrioles/centrosomes) which consist of  microtubules in a 9+3 pattern are responsible for making up the spindle used in separating chromosomes during mitosis and meiosis. Aneuploidy (having one extra or one less chromosome) results from nondisjunction, whereby one or more pairs of chromosomes do not separate as they should during mitosis or meiosis. Thus down syndrome results when a cell does not separate the correct amount of chromosomes into its cell and fails to commit apoptosis.

c.       Autosome & Steroid- As a result of nondisjunctions with autosome chromosomes, alterations occur during the development of certain phenotypes. For example in XXY males who make less testosterone and more estrogen than normal males which may result in short0term memory, learning disabilities, feminizing effects, low sperm counts, high pitched voice, etc. These individuals may receive testosterone injects –sterioids- in order to reverse the feminizing effects.

d.      Polygenic & Glycocalyx- Polygenetics pertain to the combined action of alleles of more than one gene, some traits, which are predispositions to different heart diseases, hypertension, etc as a result of genetic disorders. The glycocalyx also includes the cell-adhesion molecules that enable cells to adhere to each other and guide the movement of cells during embryonic development. It functions for protection, immunity to infection, defense against cancer, transplant compatibility, cell adhesion, inflammation regulation, fertilization, and embryonic development which are important to preventing genetic disorders leading to a variety of polygenic diseases.

III.  The law of segregation says that alleles in homologous chromosomes separate or segregate during gamete formation and unite at fertilization.  It consists of diploid cells that have pairs of genes on homologous chromosomes. The 2 genes of the pair will separate from each other during meiosis and thus be separated into different gametes. The law of independent assortment says that alleles in nonhomologous chromosomes will separate during the formation of gametes. When meiosis ends, and the pairs of homologous chromosomes have migrated to opposite poles. The chromosome which goes to which pole depends on its previous orientation which is random. This results in traits and chromosomes which are inherited independently/transmitted to the offspring independently despite previously  beings gene pairs. After meiosis the law of segregation deals with gametes with one version of each chromosomes which come together to form the zygote with one gene from each parent while the law of independent assortment occurs during metaphase till meiosis ends resulting in an independent distribution of chromosomes.

Chapter 10 Mitosis/Meiosis Work

Derek Lee

Mr. Hillegas

Ap Biology

4 February 2011

Chapter 10 Cell Reproduction Work

II.

1.      Homologous and duplicated chromosomes – Together with 23 chromosomes from each parent, 23 homologous pairs are formed. These homologous pairs are duplicated in the processes of mitosis or meiosis for either cellular reproduction, growth, and repair, or sexual reproduction. The results of mitosis form 2 somatic diploid cells, while meiosis results in 4 autonomic haploid male or female gametes.

2.      Kinetochore and Microtubule Organizing Center – During Metaphase I of meiosis when the tetrads line up long the metaphase plant, spindle fibers forms and MTs attach to kinetochores. These kinetochores shorten pulling apart the tetrads to opposites poles as the microtubules deploymerize.

3.      Haploid and Somatic – Somatic cells include all cells except sex cells. They are the cells which undergo mitosis for cell reproduction, growth, and repair as opposed to autonomic, or sex cells which undergo mitosis, thus producing 4 gametes with a haploid number of chromosomes.

4.      Nucleosome and Dehydration reaction- Nucleosomes consist of subunits of chromatin composed of a short length of DNA wrapped around a core of histone proteins. Dehydration reactions or condensation reactions refer to the use covalent bonds to join two molecules into a larger  molecule. These bonds help coil histones as they form bonds between peptide bonds.

III. Sorting of Chromosomes

A.    Meiosis I

1.      Prophase 1- Chromosomes become visible as threadlike forms, each pairs with its homologue and swaps segments with it.

a.       Microtubules form spindles, centrioles (if present) move to opposite sides of nuclear envelope.

b.      Nuclear envelope begins to break up

2.      Metaphase I – MTs attach to each type of chromosome, chromosomes line up at metaphase plate.

a.       MTs begin to pull apart chromosomes

3.      Anaphase I – Microtubules attached to each chromosome shorten and move toward spindle pole

a.       Other MTs extend from poles and overlap at equator and push the poles father apart

b.      Pushing driven by proteins

4.      Telophase I – On of each type of chromosome on complete opposite sides of poles.

a.       At some point the cytoplasm dives forming two haploid cells

b.      All chromosomes are still duplicated

B.     Meiosis II

1.      Prophase II- Spindle forms in each haploid cell while MTs move one member of pair of centrioles to opposite sides of each cell.

a.       MTOCs attach to one chromatid of each chromosome.

b.      Its sister chromatid becomes tethered to opposite pole

2.      Metaphase II – Chromosomes line at metaphase plate and MTs from both spindle poles begin to separate the sister chromatids

3.      Anaphase II – Attachment between sister chromatids of each chromosome breaks

a.       Each MTs continue to move chromosomes to opposite sides of the poles while MTs push the poles apart.

b.      Chromosomes ends up near each pole, one of each type of chromosome is present in each parcel

4.      Telophase II – Four nulei form as a new nuclear e nvelope encloses each cluster of chromosomes

a.       After cytoplasmic division each of the daughter cells has a haploid number of chromosomes.

10.4 –

A. During prophase I of meiosis the duplicated chromosomes in a germ cell are in a thread like form with little space in between.                                                                                                    1. This tight, parallel orientation favors crossing over, a molecule interaction between a chromatid of one chromosomes and a chromatid of the homologous partner.                                     2. The DNA strands break and seal in such a way that the outcome results in two “nonsister” chromatids which leads to recombination among genes of homologous chromosomes.                             3. This results in slightly different forms of alleles and thus each crossover event is a chance to swap slightly different versions of heritable information on gene products or produce variation in traits among offspring.

B. Metaphase I Alignments                                                                                                                            1. During Metaphase I, Microtubules from both poles now align all duplicated chromosomes at the metaphase plate.                                                                                                                       2. MTs attach to first chromosome they contact = random tethering and subsequent positioning of each pair of maternal and paternal chromosomes at metaphase plate.                                     3. During Anaphase I, duplicated chromosomes = move away from homologous partner = either partner can end up at either spindle pole.                                                                                             4. Result of such events leads to different combination of maternal and paternal traits in each new generation.

10.6

While Mitosis maintains the parental chromosome number, meiosis halves it, to the haploid number. Miotic cell division is the basis of asexual reproduction among eukaryotes. It is the basis of growth and tissue repair of multicelled eukaryotic species. Meiotic cell division is a required step before the formation of gametes or sexual spores.

Similarities: Both processes undergo prophase, metaphase, anaphase, and telophase with similar processes and organelles i.e. MTOCs, spindle fibers, etc. Both have cytokinesis that occurs during telophase. Mitosis and meiosis only occurs in eukaryotic cells.

Differences: Occurrence of crossing over happens in meiosis but does not happen in mitosis.

-Meiosis occurs specifically in humans, animals, plants, and fungi, while mitosis happens in all organisms.

-Meiosis produces 4 daughter cells (4 haploid) while mitosis produces 2 (2 diploid) daughter cells.

-Meiosis produces genetic variation, is sexual reproduction, requires 2 divisions, pairs homologues and undergoes two series of prophase, metaphase, anaphase, and telophase. Mitosis produces identical genes, is asexual reproduction, undergoes 1 series of division, does not pair homologues, and undergoes one series of prophase, metaphase, anaphase, and telophase.

-Meiosis produces male and female eggs/sperms while mitosis produces all cells other than sex cells

Chapters 45 and 47 work

Derek Lee

Ap Biology

22 January 2010

Chapters 45 and 47 Work

II. Connections

a.       Carrying Capacity and Biotic Potential – In situations that are ideal where there is no predation, lack of vital resources, shelter, food, etc, a biotic potential which is the maximum rate of increase per individual for any population that is growing under ideal conditions occurs. However, in reality, these things to not normally exist in nature and thus the sustainable supply of resources a habitat has will determine the population size. This sustainability of resources determines the carrying capacity, which is the maximum number of individuals of a population that a given environment can sustain indefinitely.  

b.      Organisms of an ecosystem are classified by their functional roles in a hierarchy of feeding relationships called trophic levels. It is basically who its whom and the transfer of energy from one level to the next. Biological magnification shows the concentration of a slowly non/degradable substance in body tissues as it passed along food chains i.e. DDT as it is passed from one trophic level to the next thus also passing down the toxin from one level of animals to the next.

c.       Like consumers, detritivores rely on autotrophs in order to decompose organic matter. Autotrophs capture energy from the sun whom themselves become energy for herbivores, and then consumers. Once plants and consumers die, they begin to decay and their remains become an energy and food source for detritivores.

d.      The mitochondria of living organisms such as plant and humans produces metabolic waste which is released as CO2. Atmospheric molecules of carbon dioxide, water, nitrous oxide, etc are among the main players in interactions that affect global temperature. Collectively these “greenhouse gases” act as pane glasses in a green house which impede the escape of heat energy from Earth into space thus causing the temperature to rise.

III. a. Outline 45.4 Limits on the Growth of Populations

A.    Density-Dependent Limiting Factors

1.      Large and growing populations require a substantial amount of nutrients among other factors to continue to prosper; otherwise risk death

2.      Limiting Factor – Any essential resource that is in short supply.

3.      i.e. food, mineral ions, refuge from predators, living space, absence of pollutants, etc.

4.      One factor alone is often enough to put brakes on population growth.

B.     Carrying Capacity and Logistic Growth

1.      The resources available to a small population of individuals dispersed through a habitat decreases as the population increases in size – growth rate declines

2.      Carrying capacity – the maximum number of individuals of a population that a given environment can sustain indefinitely.

3.      Logistic Growth – shows how carrying capacity may affect population size by changes in growth vs.  number of individuals and unused resources.

4.      When either exponential or logistic growth leads to overcrowding, abiotic and biotic factors function as density-dependent controls – reduce odds for individual survival.

C.     Density-Independent Limiting Factors

1.      Density-independent factors- Any factors that cause more deaths or fewer births regardless of population density.

2.      i.e. availability of a vital resource, exert control after populations become too dense as a result of exponential/logistic growth.

3.      Other factors exert control independently of population density.

b. Summarization of 3 curves & example

1. Type I curves reflect high survivorship until fairly late in life, then a large increase in deaths. For example elephants which give birth to 4-5 calves in her lifetime and devotes several years to parenting each one. Type one curves are similar to human populations where populations have access to good health care services.

2. Type II curves reflect a fairly constant death rate at all ages. They are typical of organisms just as likely to be killed or die of disease at any age, such as lizards, small mammals, and large birds.

3. Type III curves signify a death rate that is highest early in life. They characterize species that produce many small offsprings and do little, if any, parenting. Examples include sea stars and marine invertebrates, insects, fishes, plants, and fungi.

c. 1. The age structure diagram for a population undergoing negative growth would look much skinnier than other graphs, much like the outline of a small fish. Populations experiencing negative growth have nearly equal male-female rations at youth but begin to shift towards females as the population matures.

2. Populations undergoing almost no growth have the shape of the empire state building. The graph is proportional to that of a sky riser that becomes skinnier at the top. The female to male ration remains nearly constant from birth to death.

3. A population undergoing rapid growth has a very large birth growth which consistently becomes smaller at a rapid rate at each level of maturity. By the end of the age graph, the post-reproductive graph is extremely small in proportion to the pre-reproductive years.

4. A graph that grows slowly is very similar to a graph of rapid growth. The main difference is the rate and size at which the graph changes from the pre-reproductive years to post-reproductive years. The graph of slow growth remains more uniform though the changes in age are more subtle. Also, graphs of slow grow have populations which live longer than those of rapid growth which, while growing more rapidly, have populations which also die more quickly.