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The protein albumin that surrounds the yolk of an egg is a clear liquid when raw and a white solid when cooked. In one or two sentences, explain why cooking causes this change.
When a protein is heated above a critical temperature, it begins to lose its three-dimensional structure. When the secondary, tertiary, and quaternary structures of a protein break down, as they will when excessively heated, the structure of the protein is permanently destroyed.
Cells are made up mostly of water. Explain why the specific hear of water is important to a cell.
Because water has a high specific hear capacity, its temperature changes very slowly in response to energy changes. As a result, metabolic activities occurring in the cell that release or absorb energy do not significantly change the temperature of the cell, allowing the internal temperature of the cell to remain fairly constant.
A nucleic acid molecule has a distinct 3' and 5' end. Explain the significance of these ends during the assembly of a double-helix DNA molecule.
A double-helix DNA molecule consists of two single-strands of DNA. The base paring between nucleotides requires that the two strand s are arranged in opposite directions, or antiparallel.
Explain the significance of temperature and the presence of an enzyme on the rate of a reaction.
Both temperature and the presence of an enzyme increase the rate of a reaction. Because molecules are moving faster at higher temperature, there are more collisions and therefore more reactions. As a catalyst, an enzyme speeds up reactions by facilitating the coming together of the reactants(thus lowering activation energy.) at 45 degrees, the influence of the enzyme is eliminated because the high temperature denaturizes it and the reaction rate falls back to the rate that occurs in the absence of an enzyme.
The structure of an enzyme.
Enzymes are globular proteins. Proteins, in turn, are polymers of amino acids-chains of amino acids, bonded to each other by peptide bonds. The general formula for an amino acid is a central carbon atom bonded to an amino group(-NH2), a carboxyl group, and a hydrogen atom that varies with each of the 20 amino acids. The individual amino acids in a protein interact with one another, giving the protein special spatial and functional characteristics. These characteristics impart to an enzyme unique attributes that allow it to catalyze specific reactions of specific substrates. Four features of a protein. Primary structure is the kind and arrangement of amino acids in the protein. Secondary originates from hydrogen bonding between amino and carboxyl groups of amino acids. Secondary is three dimensional shape of a helix or a pleated sheet. Tertiary has interactions include hydrogen bonding and ionic bonding between R groups, and a disulfide bridge between two cysteine amino acids. The summation of all of the interactions gives enzymes a globular shape.
How enzymes function
It speeds up the rate of, or catalyzes, a reaction. The induced-fit model describes how enzymes work. The specific active sites within the enzyme to which substrate molecules weakly bond. When substrate molecules bond to the active sites, the enzyme changes shape in such a way as to reduce the activation energy required for a bond to from between the substrate molecules. With less energy required, bonding proceeds at a faster rate.
How enzymes are regulated.
Allosteric enzymes are controlled by allosteric effectors, substances that bind to the enzyme and inhibit or activate the enzyme. Sometimes an allosteric inhibitor is a product of a series of reactions partly catalyzed by the allosteric enzyme. This is an example of feedback inhibition. In competitive inhibition, an inhibitor binds to the active site, competing with substrate molecules. As a result, the activity of the enzyme is inhibited. Some toxins and drugs are example. Environmental factors also contribute to the activity of enzymes. For example, pH and temperature.
The membranes of the RER have a very large surface area. Describe how a large surface area aids the activities of the structure.
The large surface area of the RER provides abundant space for the embedded ribosomes and the production and modification of proteins.
The membrane provides a flexible boundary to the cell. Describe the differences you would expect to find in the makeup of the membrane for a plant cell in a leaf growing with full exposure to the sun compared to the one growing in the shade.
The flexibility of the membrane is influenced by the relative numbers of saturated and unsaturated fatty acids in the phospholipids. More phospholipids with unsaturated fatty acids would be found in shade leaves because the bend cause by the double bonds in the unsaturated fatty acids increases the separation of the phospholipids, which increase the membrane's flexibility in response to cooler temperatures.
Glycoproteins produced in the RER may ultimately be exported from the cell. Describe the pathway of the glycoprotein from the ER to the outside of the cell.
After the protein is produced by a ribosome on the membrane surface of ER, the ER attaches a carbohydrate to the protein and packages the glycoprotein within a vesicle. The vesicle the transports the glycoprotein to a Golgi apparatus, where is may undergo additional modification. The modified glycoproteins is again packages into a vesicle that transports the glycoprotein from the Golgi apparatus to the membrane, where it is exported by exocytosis.
The structure of the plasma membrane.
It is composed of a phospholipid bilayer. A molecule of phospholipid consists of two fatty acids and a phosphate group attached to a glycerol component. In plants, bacteria, the membrane deposits cellulose or other polysaccharides on the outside of the membrane to create a cell wall.
The various ways in which the plasma membrane permits interactions with the outside environment.
Membrane is selectively permeable membrane. The extracellular matrix in animal cells, consisting of the polysaccharides of glycolipids, recognition proteins, and other glycoproteins, provides adhesion or participates in cell-to-cell interactions.
Compare and contrast the cellular characteristics of prokaryotes and eukaryotes.
Same: membrane, ribosome, and DNA. Some pro has cell wall.
Different: DNA is packaged differently. Pro ribosomes are smaller. Size of a cell. No mitochondria.
In the process of alcohol fermentation, 2NADH molecules are converted to a NAD+ as energy from the NADH is used to drive the formation of ethanol. Why there is a need to add energy to a process whose purpose is to extract energy from glucose.
O cannot proceed and NADH accumulates without o2. No NAD for glycolysis. Fermentation generate NAD from NADH and can be used in glycolysis to generate ATP.
The mitochondrion has two phospholipid-bilayer membranes: an outer membrane and an inner membrane. Why two membranes are necessary.
H pass through membrane. Creates proton gradient, drives the movement of protons thru ATP synthase to make ATP.
Discuss the Krebs cycle and oxidative phosphorylation. Specifically address ATP and coenzyme production, the location where these biosynthetic pathways occur, and chemiosmosis theory.
a. Krebs cycle and oxidative phosphorylation are oxygen-requiring process involved in obtaining ATP form pyruvate. Pyruvate combines with coenzyme A, 2 e and 2 H removed from pyruvate combine with NAD to from 1 NADH+H. CO2 is released. The end product is acetyl CoA. Acetyl CoA combines with OAA to form citrate. A series reaction occur, 3 NADH, 1 FADH, 1 ATP form. OAA reacts with acetyl CoA, Krebs reactions as a cycle. Energy of N and F make ATP in oxidative phosphorylation. And then the numbers of ATP each generated.
b. Both occur in mitochondria. K at matrix. ETC embedded in the inner mitochondrial membrane. O at cristae membranes.
c. Chemiosmosis describes how ATP is generated from ADP+P. During O, H are on the outside of cristae. The excess number of H in intermembrane space creates pH and electric gradient that provide energy to generate ATP as H pass through ATP synthase.
Describe, at the molecular level, how cell extract energy from starches, proteins, and lipids by the process of aerobic respiration.
Starch are glucose. Enzyme break down starches to glucose, which then enter the glycolysis. Glucose enter glycolysis in the beginning and fructose (disaccharides) enters later. Lipids are hydrolyzed to glycerol and fatty acids- components produce acetyl CoA in enzymatic reactions. Proteins are hydrolyzed to amino acids that converted to CoA, OAA, and other Krebs cycle intermediates.
Explain, at molecular level, why many organisms need oxygen to maintain life.
O2 is final accepter of electrons at ETC in O. No o2, no ATP, on OP, no KC.
B. Explain, at molecular level, how some organisms can sustain life in the absence of oxygen.
Regenerate NAD so that glycolysis can continue and produce 2 ATP without o2.
There are a variety of light-absorbing pigments in chloroplasts. The purpose of having a variety of light-absorbing pigments.
Different pigments absorb different range of wavelength light energy. Allows cell absorb more light energy than only one light-absorbing pigment.
During noncyclic photophosphorylation, e from the splitting of water populate photosystem II. Where these electrons from water eventually end up.
After becoming energized in P I, the e form NADPH. Then, NADPH pass e to Calvin cycle, they regenerate RuBP(so the Calvin cycle can repeat) and partly to the formation of carbohydrates.
Calvin cycle: 6CO2+6RuBP-12PGA-12G3P-10G3P and 2G3P+glucose-6RuBP
Protons concentrate inside the thylakoids. Explain the purpose of this proton buildup.
Protons in the thylakoid space create pH and electrical gradient across thylakoid membrane. The gradient drives the movement of protons thru ATP synthase which make ATP.
Describe the biochemical pathways of the light-independent and light-dependent reactions in C3 photosynthesis
Begin with a molecule of H2O and CO2 and end with a molecule of glucose.
Photosynthesis fix inorganic carbon dioxide into glucose by water and light energy, pigments chlorophyll a and b absorb light energy of different wavelengtes.P700 at cyclic photophosphorylation which is photosystem I. 2 excited e absorbed by primary e acceptor like cytochromes. The energy form e bound with ADP and make ATP. The process is 2 e per turn. Noncyclic photophosphorylation is photosystem II. P680 energizes 2 e, 2 e go through e acceptor and pass ETC produce average 1.5 ATP and then return to PI. 2 e also combine with 2H to make NADPH. Water molecule is split producing 2e, oxygen is released. Calvin cycle combine with CO2, NADPH, and ATP to form G3P and RuBP. 6 CO2=2G3P. 2 G3P= glucose.
Although there are significant differences among the four receptor protein mechanisms, two aspects of their activity are the same. Describe the two aspects of their mechanisms that are the same.
Each of the receptor proteins requires activation by the binding of a ligand. Also, the binding of the ligand to the receptor protein causes a conformational change in its 3D structure.
Although both a protein kinase receptor and a G protein-coupled receptor can phosphorylate a cytoplasmic protein kinase, they do it in very different ways. Contrast how these two signaling mechanisms phosphorylate a protein kinase.
Protein kinase receptor directly phosphorylates and thus activates a cytoplasmic protein kinase. G protein is indirectly responsible for activation. GPCR activates a membrane-bound G protein, and then activates a second membrane-bound enzyme, then activate a protein kinase.
A. Ligand-gated ion receptor.
Ligand-gated ion receptor receives signal. Receptor channel opens and ions pass through. Ions initiate chemical response. Ligand-gated ion receptor deactivated when ligand detaches from receptor. Acetylcholine, a neurotransmitter that is the signaling molecule that transmits nerve impulses between nerve cells.
G protein-coupled receptor (GPCR).
It receives signal. GPCR activates G protein by exchanging a GTP for a GDP. A subunit of G protein binds to effector protein. Effector protein initiates response, enzymatic activity or second messenger cAMP, IP3, or DAG. GPCR signaling is deactivated when GTP is hydrolyzed. Glycogen breakdown in muscle and liver cells is an example of a cAMP signaling pathway.
Receptor tyrosine kinase (RTK)
it receives signals and two RTKs associate.2 RTK phosphorylates each other. Relay protein is phosphorylated. Relay protein imitates transduction pathway to cellular response. Deactivated by dephosohorylation or receptor protein isolation.
D. Intracellular are proteins that occur in the cytoplasm or nucleus.
Many of the activities that occur during mitosis and meiosis are similar. Describe one stage of meiosis that is distinctively different from mitosis.
During chromosome alignment in metaphase I, homo chromosomes pair on the equatorial plate and subsequently homologues separate to opposite poles. In contrast, during the same phase of mitosis, the chromosomes all line up and chromatids separate to opposite poles
How genetic variation is created by meiosis.
Crossing over during prophase I produce chromosomes with genetic material from both parents. The joining of gametes during sexual reproduction creates genomes in offspring that are unique.
What goes wrong when a cell is overtaken by cancer?
When DNA of a cell is damaged by radiation or chemicals, genes that produce protein that regulate cell division may have mutated. The protein may not trigger DNA repair and damaged DNA will be passed on to daughter cells. Damaged DNA may result in further breakdown of cell cycle regulation and the cell line may begin dividing without control, thus becoming cancerous.
The stages of mitosis, cytokinesis, and other phases of the cell cycle.
Prophase, chromatin condenses into chromosomes and the nuclear envelope and nucleolus disappear. Centrioles go to opposite, microtubules develop to form spindles. Metaphase, microtubules have pulled the chromosomes so that they are all lined up on the metaphase plate. Anaphase, sister chromatids are separated and pulled to opposite by microtubules of the spindle. Telophase, nuclear membranes appear and chromosome diffuses into chromatin. Cytokinesis, the dividing of the cytoplasm, begins during telophase. G1, the first period growth. S, a second DNA molecule is replicated. G2, the cell prepares for M.
Factors that induce cells to divide.
Cell size limited by s-to-v and genome-to-v ratio. As s-v ratio smaller, the ability of membrane provides a surface large enough to meet the import and export decrease. checkpoints determine whether cell activates should continue. Cell division also depends of the presence of cyclin-dependent kinases which activate proteins that regulate cell cycle. Cell cycle is influenced by growth factors.
Factors that might contribute to abnormal cell divisions, such as cancer.
Enzymes, induce specific activities that prepare the cell for division, affected by environmental factors. A cell that has become cancerous is because the normal cell cycle checkpoints and other regulatory mechanisms fail. For example, cancerous cells lack anchorage dependence.
The stages of meiosis.
P1, nuclear membrane breaks down, nucleolus disappears, and chromatin condenses into chromosomes. Centrioles that develop microtubules and spindle migrate to opposite, and crossing over occurs. Metaphase 1, chromosomes are aligned on the metaphase plate as humongous pair. Anaphase 1........
The function of meiotic daughter cells and the organs where meiosis takes place.
Daughter cells are haploid. In human, daughter cells are gametes, sperm and eggs, formed in testes and ovaries. Gametes fuse to form a diploid zygote, which then grows us.
contributions to genetic variation.
Crossing over, independent assortment, joining gametes.
Why males have a greater chance of expressing the color-blindness trait.
Males inherit only one X chromosome, they express all the genes on that chromosome, regardless of whether the alleles are dominant or recessive. In contrast, females inherit two X chromosomes and both alleles for a gene must be recessive in order for a female to express a recessive trait.
A form of vitamin D resistance is inherited as an X-linked dominant allele. Why females have a greater chance of inheriting and expressing the vitamin D-resistant trait.
Because females have two X chromosomes, they have two chances of inheriting a trait on that chromosome and they need only one copy of dominant allele to express the trait.
The height of an individual can be any value over a wide range, from short to tall. Describe a mechanism that can produce such continuous variation.
A trait that is produced by the expression of many interacting genes generates continuous variation in population. Also, multiple alleles of a single gene can recombine to produce many genotypic and phenotypic combinations.
Genes that are not linked.
Genes that are on different chromosomes migrate independently of genes on other chromosomes because of independent assortment.
Genes that are linked.
They migrate together to either pole. They violate Mendel's law of independent assortment.
Occur when a gene is located on one of the sex chromosomes.
Down syndrome
Nondisjunction of the two number 21 chromosomes. The homo pair does move to opposite, both chromosomes end up at the same pole and in the same gamete. One gamete with two 21 chromosomes, one gamete without chromosomes. The zygote formed between this gamete and a normal gamete will have a 3 21 chromosomes child. Down syndrome consists of physical abnormalities and mental retardation.
Turner syndrome
Nondisjunction of sex chromosomes. One gamete with no sex chromosomes fuses with a normal gamete will have a single X chromosomes and express Turner syndrome that are females and exhibit physical abnormalities, including sterility.
Gene regulation in eukaryotic cells is considerably more complicated than gene regulation in prokaryotes. Describe two reasons eukaryotic organisms require a more complex approach to gene regulation.
Eukaryotic are multicellular. Gene regulation must be able to regulate gene expression specific to cell type. Eukaryotes have more than one chromosome, regulation of multiple genes on different chromosomes required.
In some cases, a single nucleotide mutation does not lead to the creation of a different protein. Explain how this can happen.
No new amino acid is designated if the mutation is a substitution in the third position of the mRNA codon.
Traditional fingerprints and DNA fingerprints are both used to identify suspected criminals. Can either of these two techniques distinguish identical twins?
Yes. Tradition fingerprints can because identical twins have different dermal ridges due to genes regulation that is influenced by environmental factors. DNA fingerprint represents "raw" genetic material that cannot distinguish identical twins.
Protein synthesis. DNA to RNA. RNA polymerase associates with various regulating transcription factors, attaches to DNA at a promoter region on the DNA. RNA polymerase directs RNA nucleotides to base-pair with the DNA fragment that represents the gene. Products are RNA-mRNA, tRNA, and rRNA.
RNA processing
The mRNA contains the code for the polypeptide. Noncoding sequences called introns are removed and mRNA is stabilized with 5' cap and a poly-A tail then moves to the cytoplasm.
In cytoplasm describes the actual assembly of amino into proteins. Ribosomes that consisting of rRNA and proteins attach to the mRNA. Then tRNA attaches ribosome. Different tRNA describes different amino, called anticodons. Ribosomes direct the pairing of the anticodons of tRNA with appropriate triplet regions of the mRNA, called codons. Each mRNA codon for amino acid. Ribosome provides binding sites to incoming tRNA that brings the appropriate amino acid as dictated by the codon sequence on the mRNA. New tRNA arrives, old released. Ribosome moves over one binding site, process repeat until stop codon.
Protein folding
Once released, the amino acids in the polypeptide may interact with one another giving the polypeptide secondary and tertiary protein structures. Secondary, tertiary..... Polypeptide may be an enzyme that can regulate a reaction that will produce some end product or trait.
Destroy cells. Consist nucleic acid core and a protein coat. When DNA virus enter a cell the use metabolic machinery and raw materials of the cell to make more viral DNA and viral protein coats. The DNA and protein then assemble into hundred new viruses that kill the cell.
No directly. Cause diseases by producing toxins that will affect the normal metabolism of the host, disease results.
Describe how gene regulation occurs in
a. Bacterial cells
Trp operon: repressible operon, normally on, build organic molecules, organic molecule produce acts as corepressor that binds to repressor to activate it. From on to off. No corepressor, inactive repressor. Corepressor, active repressor.
Lac operon: inducible operon, normally off, catabolic, break down food for energy. No inducer, active repressor, operon off. Inducer, inactive repressor, operon on.
b. Eukaryotic cells
RNA polymerase attaches to a promoter region (TATA boxes) on the DNA to begins to unzip the DNA into two strands. RNA polymerase assemble RNA nucleotides using one strand of the DNA. 5' to 3'. RNA polymerase reaches a special sequence of nucleotides that serve as a stop sign.
Although muscles attach the human ear to the skull, few people can actually use these muscles to move their ears. Why the muscles are present if they serve no purpose.
Inherited from ancestors in whom they served a function.
"Species evolve because they have to adapt to survive." Why this is wrong.
Species do not have to adapt. Adaptations are inherited, an individual either inherits an advantageous trait or does not.
Fingerprints, created by dermal ridges on fingers, are an example of neutral variation. The patterns vary among individuals, but differences have no selective value. If variation in fingerprints represents neutral variation, does this mean that the dermal ridges on fingers have no selective value?
It does have value. Provide friction to allow for a better grip. The pattern is not important, but the presence of ridges is important.
Mutations add new alleles, increase variation, introduce new traits that are more successful that others in the population. Variation mix up existing alleles through genetic recombination and mutation is raw material for variation.
Genetic drift
Cause allele frequencies to change. Genetic drift describes random changes in allele frequencies. Big influence when population is small.
Gene flow
The movement of alleles between populations. Occur when immigrate, bring alleles into the population. Emigrate, removing alleles from the population.
Nonrandom mating
Changes in allele frequencies. In sexual selection, allele frequencies increase if they produce traits that give individuals a better chance of obtaining a mate. Inbreeding is another one.
Allopatric speciation
Geographic barrier occur. Divide population into different environment. Different environmental conditions, different favor traits, different genetic drift and mutation, different change in mutation.
Sympatric speciation
No geographic barrier. Reproductive isolation occurs. Reasons: polyploidy, 3n. interbreeding.
Adaptive radiation
A population is introduced to an area where many geographic conditions are available. Finches inhabit the Galapagos Islands.
Describe mechanisms that maintain reproductive isolation for
a. Prezygotic
Prevent fertilization. Habitat isolation, species do not meet each other. Temporal isolation, mate during different times. Behavioral isolation, display wrong signals then not recognize another as mating partner. Mechanical isolation, incompatible structures. Gametic isolation, male do not survive.
b. Postzygotic
Prevent formation of fertile progeny. Hybrid inviability, zygote die. Hybrid sterility, hybrids have no reproduce skills. Hybrid breakdown, offspring reduce fertility.
Discuss each of the following as they relate to speciation.
a. Geographic barriers
Isolation, evolution differ, species differ.
b. Polyploidy
Wrong set chromosome, reproductively isolated, occurs only one single generation.
c. Sexual selection
No random mating. Sexual selection results in attributes that improve success traits that are attractive to females.
Variation among individuals
Natural selection favors individuals with traits increase their fitness. If all individuals are identical, no one individual will be more fit. No variation, no natural selection.
Heritability of traits
No heritable, it does not matter how much it may increase fitness because it cannot be passed on to the next generation.
Competition for resources
If there are unlimited resources and unlimited availability of mates, differences among individuals won't have any effect on their ability to produce offspring. No competition, no natural selection, no evolution.
Discuss how each of the following influenced the origin of living organisms.
a. Primordial atmosphere
Originated from outgassing of the molten interior of the planet and consisted primarily of CO2 and N2, but little or no O2
b. Photosynthesis
Produce oxygen
c. Oxygen and the ozone layer
Incoming UV lights absorbed.
d. Endosymbiotic theory
Describes how eukaryotic cells originated from a mutually beneficial association among various kinds of prokaryotes, like mitochondria, chloroplasts.
The phrase, " a rotten apple spoils the barrel," originates from the observation that a ripened fruit placed in a container of many unripened fruits will lead to their quick ripening. How one ripe fruit can induce other fruit ripen.
Ethylene is a hormone that accelerates fruit ripening. Because it is a gas, it affects not only the fruit from where it originates, but nearby fruit as well.
Some plants do not use daytime length or length of night as a signal to initiate flowering. Describe an environment in which daytime length would not be a useful signal for flowering.
Equatorial regions do not have significant differences in day and night lengths during the year. Thus, day and night lengths would not be useful for identifying the beginning of a particular season.
Describe the movement of water into roots and from roots to leaves.
Enter roots through root hairs, hair-like extensions of cells that increase the absorptive surface area of roots. Water moves toward xylem cells through cell wall. Water in the leaves is used for photosynthesis or is lost by transpiration. Cohesion-tension theory
Plants respond to environmental stimuli in various ways.
a. Describe the mechanism of one plant response to a biotic stimulus.
Structural defenses: sharp leaves prevent for eating. Chemical defenses; release toxic to discourage browsing.
b. Describe the mechanism of one plant response to an abiotic stimulus.
The response of light, the response to gravity by stems and roots, response to touch.
The human immunodeficiency virus (HIV) that causes AIDS attacks white bold cells. Why this makes it difficult for the immune system to defend against the HIV.
HIV attacks helper T cells. When helper T cell becomes infected, more T cells produced. More T cells, more of them become infected by HIV.
Eating salty foods often makes people thirsty.
Absorb the salt, solute concentration increase, become hypertonic.
Target cells recognize hormones.
Hormone binds receptor, receptor activates transcription of genes. Receptor trigger the production of second messenger.
B cells recognize antigens.
B cells have special antigen receptors on their membrane. It has different receptors.
Postsynaptic membranes recognize neurotransmitters.
Neurotransmitter diffuses across the synaptic cleft to the postsynaptic membrane, binds with receptor, the binding cause an influx of Na+ or efflux of K+.
Describe the biochemical events associated with the transmission of nerve impulses.
a. Along neurons
Resting potential and graded potentials. Depolarization and action potentials. Repolarization. Hyperpolarization. Refractory period.
b. Across synapses
A gap separated adjacent neurons. Calcium gates open, synaptic vesicles release neurotransmitter that binds with receptor. Postsynaptic membrane is excited or inhibited. The neurotransmitter is degraded and recycled.
In humans, describe the digestion and absorption of each of the following.
a. Proteins
Broken down into amino acids.
b. Starches
Into glucose molecules
c. Fats
Into glycerol and fatty acids
When LH and FSH drop during the menstrual cycle, the corpus luteum deteriorates, estrogen and progesterone production stops, and the menstrual cycle begins again. Should egg become fertilized and implanted in the endometrium, explain how the endometrium is maintained if the corpus luteum is no longer viable and secreting estrogen and progesterone?
should implantation occur, the implanted embryo secretes hGG that maintains the corpus luteum and prevent it from deteriorating and allowing it to continue its production of estrogen and progesterone.
When cells die from injury, they often burst and release their contents into the surrounding extracellular fluids. How apoptosis, programmed cell death, is different.
apoptosis is planned, orderly process in which proteases break down cellular structure. fragments of these structures remain packaged inside membrane, allowing for easy eaten by neighboring cells.
Compare and contrast sperm and egg production in humans.
compare: similar hormones. LH for sex organs. FSM for development of the gametes.
contrast: female has 1 viable egg and 3 nonfunctional eggs, male has all viable sperms
Jet lag is a feeling of fatigue, sleepiness, or insomnia that is often experienced by air travelers after long-distance flights.
Cyclic variations in melatonin levels increase in darkness and falling in daylight to maintain a 24 hour circadian rhythm. Jet lag occurs as a result of the change in light after crossing multiple time zones.
A species of fly that does not bite or sting alternating yellow and black stripes on its body. Explain the value these marking s bring to these harmless flies.
They fool predators into thinking that they are dangerous because of the color
A keystone species has a strong influence on the health of a community. Are you more likely to find a keystone species in a large, complex community or in a small , simple community?
Small. Large has many interacting populations and the removal of one species can be replaced. Keystone species cannot be replaced because of the negative consequences to the community.
Describe the process of succession for a lake as it develops into a forest.
Primary succession, a newly exposed surface. Secondary succession, community changes the habitat to become more suitable to new species. Final, stable community retains unchanged until destroyed by nature event. Then process begins again
Compare and contrast the succession of a lake and the eutrophication of a lake polluted by fertilizer or sewage.
Eutrophication is the bad one lake.
Explain how two closely related species can occupy the same habitat, seemingly competing for the same kinds of resources.
Niche things, god knows, bio s so hard
Describe the cycling of nitrogen in an ecosystem.
80% N2 in atmosphere. Nitrogen fixation converse N2 to NH4+ by bacteria in the soil or in the legumes' roots molecules. Nitrification is inverse. N2 to NO3- by lightning. Denitrification is inverse. From NH4 or NO3, plants make amino acids and nucleic acids. When animals eat the plants, they obtain nitrogen. When they break down protein, they produce NH3 that is toxic. When animal and plant die, they decompose and convert to NH4 that good for plants again.