BIO 105 exam 2
At the end of meiosis, how many cells are formed (from one cell)? Are the cells haploid or diploid?
-4 genetically different cells -Haploid = contains only one copy of each chromosome
Determine each of the following cells is haploid or diploid.
-An egg: haploid -A cell from your liver: diploid -A zygote: haploid -A sperm: haploid -A cell from your heart: diploid
The number of organisms goes down with each step up in the trophic levels. Why?
-Because the amount of energy at each trophic level decreases as you move up the trophic pyramid. -The size of each layer represents the amount of energy available at that trophic level -Only about 10% of the energy taken in by the individuals at one trophic level is passed onto individuals at the next -The bulk of energy received from the previous level is used by the organism who obtained it; this energy is released as heat energy and lost to the ecosystem
Energy is described as having a one-way flow through an ecosystem. What does this mean?
-Begins with the sun; starts at primary producers to various consumers
What are the inputs and outputs of photosynthesis? Write the equation.
-Carbon dioxide + water +(energy) → Sugar + oxygen -CO2 + H2O + (light energy) → Sugar + O2 -First half input; Second half output
What is the primary pigment found in the chloroplasts?
-Chlorophyll
What organelle must be present in photosynthetic eukaryotes?
Chloroplasts: function in light absorption/ photosynthesis/carbohydrate synthesis
What do food chains and food webs show? How are they similar? How are they different? Can you diagram both? Why isn't a food chain a very accurate picture of an ecosystem's trophic structure?
-Food chains: a sequence of organisms each feeding on the next, showing how energy is transferred from one organism to another; arrow points to the consumer; Pinecone → red squirrel → weasel → hawk -Food webs: a representation of the feeding relationships within a community; highly complex - consumers feed on many species; more accurate display of who eats who -Food chains aren't an accurate picture because food chains do not exist in nature. They simply show feeding relationships.
How does a plant get H2O? How does it get CO2?
-H2O from the ground -CO2 from the air
A cell biologist observes a cell under a microscope and determines that the cell contains nine chromosomes. Is this cell diploid or haploid? Based on your answer, can you predict what kind of cell this is? Explain.
-Haploid cell & because it's a haploid cell this means it's a gamete
Which organisms eat only plants? Only animals? Both? Which of organisms break down dead matter?
-Herbivore: Organisms that eat plants and other producers -Carnivore: Organisms that eat other animals -Omnivore: Organisms that eat both plants and animals -Scavenger: Organisms that feed on the remains of another organism
The practice of "eating down the food chain" refers to eating more plant material and less herbivores. Explain how this is a more efficient use of energy.
-In any pyramid, taking out a level lets you shrink to the base. -When you cut the livestock step out and eat plants directly, it takes a lot less of the plants to support you
What is nondisjunction? Give an example of a disorder caused by nondisjunction.
-It is when chromosomes fail to separate properly → Resulting gametes will have too few or too many chromosomes -Zygotes with abnormal chromosome number will usually not develop or will have abnormalities -Example: Trisomy 21 is a condition in which a person receives three copies of chromosome 21; the resulting condition is called Down syndrome
How can a karyotype be used to determine the gender of an individual?
-Karyotypes are photographic inventories of chromosomes
People are very familiar with the terrestrial (land) producers, but they are not as familiar with aquatic producers. List two aquatic producers.
-Kelp -Algae
What color of light is not used for photosynthesis? How could you know this just by looking at a leaf?
-Light in the blue/violet & orange/red ranges is absorbed -Light in the green/yellow range is reflected -Plants look green because chlorophyll reflects green light
How are mitosis and meiosis similar? How are they different?
-Mitosis is the process by which animals and plants produce somatic (body) cells -Meiosis occurs only in the reproductive cells in a plant/animal; it is the process by which animals and plants produce eggs or sperm
What are homologous chromosomes?
-Pair of chromosomes that are of the same gender -XX or YY
A common misconception is that plant cells have only chloroplasts & not mitochondria. Explain why plant cells need both, whereas animal cells have only mitochondria.
-Plant cells have mitochondria for the same reason that we do - to produce energy (more efficiently!) Specifically, mitochondria allow for a more extensive breakdown of glucose, which results in more ATP for the cell. -Also want to point out - chloroplasts do not supersede mitochondria; chloroplasts create sugar from sunlight, but plant cells still need mitochondria to break down the sugar. - Mitochondria, on the other hand, efficiently break down macromolecules, such as carbohydrates or lipids, into ATP. While the light reaction and other non-mitochondrial dependent reactions can also generate ATP, the Citric acid cycle/Electron transport chain is much more efficient at generating ATP than any of these processes.
What is the main point of photosynthesis?
-Procedures capture solar energy and convert it to chemical energy -Energy is stored in the bonds of sugar molecules
List an example of a cell in your body that undergoes mitosis. How many chromosomes does that cell have? Is it haploid or diploid?
-Skin cell -Diploid = they have two copies of each chromosome
Plants use glucose for energy the same way animal cells do. But, they also use glucose as a structural building block (i.e. to build their "bodies"). What are two important structural molecules plants make using glucose? Examples?
-Starch; Carrots -Cellulose; Tree base
What are the inputs and outputs of cellular respiration? Write the equation.
-Sugar + Oxygen → Carbon dioxide + water + energy -Sugar +O2 → CO2 + H2O + energy -Inputs: O2 travels from the lungs to the mitochondria; Food travels from the digestive system to the mitochondria -CO2 leaves the cell & is expelled from the lungs
Explain what a keystone species is. Give an example from nature.
-Term used for particularly strong interactors -Species whose activities maintain species and habitat diversity and whose effects are disproportionate to their abundance. Where the density of a keystone species falls below some threshold, the species diversity in the area may decrease, triggering ecological chain reactions, ending with degraded or simplified ecosystems. Among such are large predators. Keystone species can be thought of as having the highest per capita interaction strengths
In photosynthesis, what gaseous molecule is the base molecule from which sugar is produced?
-The Calvin cycle makes sugar from CO2
Explain what a trophic cascade is. Give an example from nature.
-The elimination of predators destabilizes ecosystems, setting off chain reactions that eventually cascade down the trophic ladder (food web pyramid) to the lowest rung, often reducing habitat complexity and species diversity - A widely known example is provided by gray wolves in Yellowstone, where extirpation (local extinction) of this large carnivore led to an irruption in the numbers of elk, causing changes in vegetation structure, species composition, and diversity. Without wolves keeping these ungulates in check, elk achieved much higher densities and shifted their behavior to a more concentrated feeding pattern, leading to the virtual disappearance of major vegetation types such as aspen and willow-beaver wetlands in some areas. Once wolves were restored to the park, over-browsed vegetation was given a chance to recover and the park's natural vegetative pattern began to return.
Why do the leaves on trees in our region turn red, orange, and yellow in autumn?
-The simple answer is that, during summer, chlorophyll in the leaves is so densely green that it hides the yellow and orange colors of other chemical compounds that are also there. But when chlorophyll begins to disappear with the oncoming cold season, the oranges and yellows are exposed. At the same time, in autumn, red chemical compounds are produced in large quantity by some trees, and these are added to the orange and yellow. The brown color is that of tannin, a waste product of the tree's life processes.
Explain why mitochondria are often called "the powerhouse of the cell."
-They're tiny organelles inside cells that are involved in releasing energy from food →Process is known as cellular respiration
Why do we need to produce sperm and eggs (gametes)? Explain.
-To make babies; reproduction
A Snickers bar contains fats, proteins, and carbohydrates. If you eat it, will your body still be able to produce ATP from it? Explain.
-When you eat a snickers bar you get sugars, fats, proteins, all kinds of stuff that can be turned into fuel, right? so your body has to convert it (using various enzyme-driven processes) into glucose-6-phosphate so that it can enter glycolysis, right? you don't just absorb glucose directly from a candy bar. you have to burn some ATPs in order to break down the components into simple sugars that can be sent through glycolysis - This is why complex carbs are 'better for you' too...your body has to burn energy to use them as fuel, the net gain of energy per moles of sugar is lower, thus there is less fuel that is made and you should be less likely to gain excess weight than if you ate an equivalent amount of straight simple sugar
Sexual reproduction produces a tremendous amount of diversity in organisms. Describe three ways in which this diversity is accomplished.
1. Independent assortment of chromosomes: Chromosomes line up by homologous pairs during meiosis; maternal and paternal chromosomes are shuffled randomly -Example: in an organism with 4 chromosomes (2 homologous pairs of chromosomes); independent assortment in humans: 2^23=8 million possible arrangements of chromosomes 2. Random fertilization by sperm and egg leads to variation: The probability that any one sperm will fertilize any particular egg is extremely small. -Example: 8 million x 8 million = 64 trillion possible arrangements of chromosomes 3. Crossing over during meiosis leads to variation: occurs when homologous chromosomes line up during meiosis 1; chromosomes can "swap" genetic material, creating hybrid chromosomes with unique combinations → increases gene variation
