Chapter 20
What is a Virus and how do they reproduce?
A virus is a nonliving particle made of proteins, nucleic acids, and sometimes lipids.
Viruses can reproduce only by infecting living cells. Inside living cells, viruses use their genetic information to make multiple copies of themselves. Some viruses replicate immediately, while others initially persist in an inactive state within the host.
What are Protists and what is the protist Dilemma?
Protists are eukaryotes that are not members of the plant, animal, or fungi kingdoms.
Protists are complicated to classify because some of them share more characteristics with plants, animals and fungi than they do with other protists. Protists display a far greater degree of diversity than any other eukaryotic kingdom and so they cannot be classified as one kingdom but rather are a collection of different clades.
What are some things plants need to survive?
The lives of plants center on the need for sunlight, gas exchange, water, and minerals
What are the three main tissue systems of plants and their functions?
Dermal tissue-protective outer covering of a plant
Vascular tissue-supports plant by transporting water and nutrients throughout (Xylem and Phloem)
Ground Tissue-Produces and stores sugars, and also help to physically support the plant- Parenchyma, Collenchyma and Sclerenchyma
What are the female and male parts of a flowering plant?
Female-Carpal which contains the Style, Stigma and Ovaries
Male-Stamen which contains the anther and filament
Compare and contrast between the two classes of prokaryotes
All prokaryotes (Archae and Bacteria) are unicellular, lack membrane-bound organelles, They are usually small, simple cells about 0.1-5µm. They also have DNA
Prokaryotes vary in their size and shape, in the way they move, and in the way they obtain and release energy,
What are the different ways protists move and reproduce?
Some protists move by changing their cell shape (amoeboid movement-Pseudopodia), and some move by means of specialized organelles (Cilia and Flagella). Other protists do not move actively but are carried by wind, water, or other organisms (spores).
Most reproduce asexually by mitosis. Others have life cycles that combine asexual and sexual forms of reproduction. (e.g conjugation and alternation of generations)
Explain the life cycle of plants
The life cycle of land plants has two alternating phases, a diploid (2N) phase and a haploid (N) phase. This shift between haploid and diploid is known as the alternation of generations. The multicellular diploid (2N) phase is known as the sporophyte, or spore-producing plant. The multicellular haploid (N) phase is known as the gametophyte , or gamete-producing plant.
What are the main organs of a plant and what functions do they serve
Roots-Anchor plants in the ground, holding soil in place and preventing erosion. Root systems often work with soil bacteria and fungi in mutualistic relationships that help the roots absorb water and dissolved nutrients. Roots transport these materials to the rest of the plant, store food, and hold plants upright against forces such as wind and rain.
Stems-Plant stems provide a support system for the plant body, a transport system that carries nutrients, and a defensive system that protects the plant against predators and disease. Stems also produce leaves and reproductive organs such as flowers.
Leaves-Leaves are the plant’s main photosynthetic organs
How do fruits form and how are seeds dispersed?
BONUS-What factors can affect the germination of a seed?
As angiosperm seeds mature, ovary walls thicken to form a fruit that encloses the developing seeds.
Seeds are dispersed by animals (if they are in fleshy, nutritious fruits), wind and water (light fruit that allows them to be carried in air or buoyant fruits for water dispersal)
Environmental factors such as temperature and moisture can cause a seed to end dormancy and germinate.
What are the types of viral infections and how do they work?
Lytic and Lysogenic
Lytic Infections-a lytic infection, a virus enters a bacterial cell, makes copies of itself, and causes the cell to burst, or lyse (lys). Bacteriophage T4 is an example of a bacteriophage that causes such an infection. Bacteriophage T4 has a DNA core inside a protein capsid that binds to the surface of a host cell. The virus injects its DNA into the cell, and the cell then begins to make messenger RNA (mRNA) from the viral genes. The viral mRNA is translated into viral proteins that act like a molecular wrecking crew, chopping up the cell’s DNA. Under the control of viral genes, the host cell’s metabolic system now makes thousands of copies of viral nucleic acid and capsid proteins. The viral DNA is assembled into new virus particles. Before long, the infected cell lyses, releasing hundreds of virus particles that may go on to infect other cells.
Lysogenic Infections-lysogenic infection, in which a host cell is not immediately taken over. Instead, the viral nucleic acid is inserted into the host cell’s DNA, where it is copied along with the host DNA without damaging the host. Viral DNA multiplies as the host cells multiply. In this way, each generation of daughter cells derived from the original host cell is infected. Bacteriophage DNA that becomes embedded in the bacterial host’s DNA is called a prophage. The prophage may remain part of the DNA of the host cell for many generations. Influences from the environment— including radiation, heat, and certain chemicals—trigger the prophage to become active. It then removes itself from the host cell DNA and directs the synthesis of new virus particles. The lysogenic infection now becomes an active lytic infection
What is the Ecological significance of protists
Autotrophic protists serve as food which helps sustain the diversity of aquatic life?
Some protists help in eliminating waste such as sewage
Some provide shelters
Many protists are involved in mutualistic symbioses, in which they and their hosts both benefit
Parasitic protists are responsible for some of the world’s most deadly diseases, including several kinds of debilitating intestinal diseases, African sleeping sickness, and malaria.
What are the key features of Angiosperm reproduction
Angiosperms reproduce sexually by means of flowers. After fertilization, ovaries within flowers develop into fruits that surround, protect, and help disperse the seeds.
Give two nutrients that plants need, one role they each play in a plant and what a deficiency in these nutrients may result in
See page 671 of textbook (once again, I got lazy sorry)
Explain the development and fertilization process in flowering plants
What is Vegetative propagation? give two examples we talked about in class
The process of fertilization in angiosperms is distinct from that found in other plants. Two fertilization events take place—one produces the zygote and the other a tissue, called endosperm, within the seed
(For more explanation, see page 699-700 pf textbook)
Vegetative reproduction is the formation of new individuals by mitosis. It does not require gametes, flowers, or fertilization. E.g stem cuttings and grafting
What are emerging Diseases and why are they so dangerous?
Give two ways each to control the spread of viruses and bacteria
An unknown disease that appears in a population for the first time or a well-known disease that suddenly becomes harder to control.
The pathogens that cause emerging diseases are particularly threatening to human health because human populations have little or no resistance to them, and because methods of control have yet to be developed. Because of their sudden appearance and resistance to existing control methods, emerging diseases are of particular concern.
Bacterial control-Antibiotics, Sterilization, Hand-washing, food storage,
Viral control-Antivirals, vaccines, hand-washing
What are the characteristics of Fungi? How do they affect other organisms in the environment?
Fungi are heterotrophic eukaryotes with cell walls that contain chitin. Their structure includes branching filaments called Hyphae, the fruiting body which is the reproductive structure of the fungus. The fruiting body grows from the mycelium, the mass of branching hyphae below the soil.
Fungi can reproduce asexually, primarily by releasing spores that are adapted to travel through air and water. Simply breaking off a hypha or budding off a cell can also serve as asexual reproduction. Most fungi also can reproduce sexually. Sexual reproduction in fungi often involves two different mating types. In Rhizopus, as in most fungi, gametes of both mating types are about the same size and are not usually called male and female. Instead, one mating type is called “+” (plus) and the other “–” (minus). When hyphae of opposite mating types meet, they start the process of sexual reproduction by fusing, bringing + and – nuclei together in the same cell. The + and – nuclei form pairs that divide in unison as the mycelium grows. Many of the paired nuclei fuse to form diploid zygote nuclei, which go through meiosis to make haploid spores. Each spore has a different combination of parental genes, and each can make a new mycelium.
HOW THEY AFFECT THE ENVIRONMENT:
Fungi are champions of decomposition. Many species help ecosystems maintain homeostasis by breaking down dead organisms and recycling essential elements and nutrients
Parasitic fungi can cause serious diseases in plants and animals by disrupting homeostasis.
Some fungi form mutualistic associations with photosynthetic organisms in which both partners benefit (Mycorrhizae and Lichen)
How are Angiosperms classified?
Using one of the classification features list the main classes and the features
Angiosperms are often grouped according to the number of their seed leaves, the strength and composition of their stems, and the number of growing seasons they live
Monocot-One cotyledon, parallel veins on leaves, flower parts are often in multiples of 3, vascular bundles are scattered throughout the stem, fibrous roots
Dicots- Two cotyledons, veins on leaves are branched, floral parts are in multiples of 5 or 4, vascular bundles in stems are arranged in a ring, possess tap root.
Woody vs. Herbaceous plants: Woody plants are made primarily of cells with thick cell walls that support the plant body. Woody plants include trees, shrubs, and vines. Plant stems that are smooth and nonwoody are characteristic of herbaceous plants. Herbaceous plants do not produce wood as they grow
Annuals vs Biannuals vs Perennials (A- grow, mature, produce seeds and die in one growing season. B-growth in first year, more growth occurs in second year including seed production and death. P-Continue to grow and replace new stems for multiple years (4-5 years))
Describe how water and sugars are transported in plants
Water- The combination of transpiration and capillary action are the major forces that move water through the xylem tissues of a plant. (Your answer should have more details ^^)
Sugars-Active transport moves sugars into the sieve tube from surrounding tissues.
Water then follows by osmosis, creating pressure in the tube at the source of the sugars.
If another region of the plant has a need for sugars, they are actively pumped out of the tube and into the surrounding tissues. Osmosis then causes water to leave the tube, reducing pressure in the tube at such places. The result is a pressuredriven flow of nutrient rich fluid from the sources of sugars (source cells) to the places in the plants where sugars are used or stored (sink cells)
What are the three/ four tropisms in plants, please explain
Geotropism thigmotropism, hydrotropism, phototropism
Phototropism-The tendency of a plant to grow toward a light source is called phototropism. This response can be so quick that young seedlings reorient themselves in a matter of hours.
Gravitropism or Geotropism- Auxins also affect gravitropism, the response of a plant to gravity. For reasons still not understood, auxins migrate to the lower sides of horizontal roots and stems. In horizontal stems, the migration causes the stem to bend upright. In horizontal roots, however, the migration causes roots to bend downward.
Thigmotropism- Some plants even respond to touch, a process called thigmotropism. Vines and climbing plants exhibit thigmotropism when they encounter an object and wrap around it.
Hydrotropism-growth towards or away from water
How do Prokaryotes reproduce and share their genetic information? Explain your answer
•Binary Fission: A fully grown prokaryote doubles its size, replicates its DNA and then divides in half producing two identical cells
•Endospore formation: In unfavourable conditions, prokaryotic cells form an endospore. The internal wall encloses some DNA and a part of the cytoplasm which forms an endospore. Endospores can survive for many years and in very harsh conditions.
Genetic Exchange:
•Conjugation: Two bacterial cells from a bridge connecting them and this allows the plasmid which contains genetic information to move from one cell to the other
•Mutations: Random changes in DNA that occur in all organisms. Mutations are inherited by the daughter cells during binary fission
Pick one out of the four phyla of Fungi and explain their features and give two examples
See page 621 of textbook
Compare and contrast between the five main classes of plants, what adaptations and features do each of them have
-Green Algae
-Bryophytes
-Vascular Plants
-Angiosperms
-Gymnosperms
(for more explanation please see chapter 22.2 and 22.3 of your textbook-I ran out of time to put the answers up)
Describe the cells that make up the main tissues of plants
Bonus question-What are Meristems
Vascular: Xylem: Tracheids All seed plants have xylem cells called tracheids. Tracheids are long and narrow, with tough cell walls that help to support the plant. As they mature, tracheids die, leaving only their cell walls. These cell walls contain lignin, a complex molecule that resists water and gives wood much of its strength. Openings in the walls connect neighboring cells and allow water to flow from cell to cell. Thinner regions of the wall, known as pits, allow water to diffuse from tracheids into surrounding ground tissue. These adaptations allow tracheids to carry water throughout the plant and distribute it to tissues where it is needed.
Xylem: Vessel Elements In addition to tracheids, angiosperms possess a second form of xylem tissue known as a vessel element. Vessel elements are wider than tracheids and are arranged end to end on top of one another like a stack of tin cans. After they mature and die, cell walls at both ends are left with slitlike openings through which water can move freely. In some vessel elements, the end walls disappear altogether, producing a continuous tube.
Phloem: Sieve Tube Elements Unlike xylem cells, phloem cells are alive at maturity. The main phloem cells are sieve tube elements, which are arranged end to end, forming sieve tubes. The end walls of sieve tube elements have many small holes through which nutrients move from cell to cell in a watery stream. As sieve tube elements mature, they lose their nuclei and most other organelles. The remaining organelles hug the inside of the cell wall and are kept alive by companion cells. Phloem: Companion Cells The cells that surround sieve tube elements are called companion cells. Companion cells keep their nuclei and other organelles through their lifetime. Companion cells support the phloem cells and aid in the movement of substances in and out of the phloem.
Ground Tissue:
Parenchyma cells have a thin cell wall and a large central vacuole surrounded by a thin layer of cytoplasm. In leaves, these cells contain many chloroplasts and are the site of most of a plant’s photosynthesis
Collenchyma cells have strong, flexible cell walls that help support plant organs. Chains of such cells make up the familiar “strings” of a stalk of celery.
Sclerenchyma cells have extremely thick, rigid cell walls that make ground tissue such as seed coats tough and strong.
Dermal Tissue:
Dermal tissue in young plants consists of a single layer of cells called the epidermis. The outer surfaces of epidermal cells are often covered with a thick waxy layer called the cuticle, which protects against water loss. Some epidermal cells have tiny projections known as trichomes. Trichomes help protect the leaf and may give the leaf a fuzzy appearance.
Bonus answer: Meristems are regions of unspecialized cells in which mitosis produces new cells that are ready for differentiation
What are the major hormones in plant, state their function and where they appear
Bonus question-What are some benefits that plants offer to humans?
Auxins-Promote cell elongation and apical dominance; stimulate growth of new roots. Produced in shoot apical stem and is transported elsewhere
Cytokinins-Stimulate cell division; affect root growth and differentiation; may work in opposition to auxins. Found in growing or maturing roots
Gibberllins- Stimulate growth; influence various developmental processes; promote germination. Found in shoot meristems, roots and seed embryo
Abscisic Acid- Inhibits cell division; promotes seed dormancy. Found in terminal buds, seeds
Ethylene-Stimulates fruits to ripen; causes plants to seal off and drop unnecessary organs, such as leaves in autumn. Found in fruits, older/ageing leaves and flowers
Plants produce food, the raw materials for our homes and clothes, and some of our most powerful and effective medicines. As well as oxygen and help eliminate Carbon dioxide waste