Biol 172 Chapters 37 & 38

What does haploid (n) mean?

Having one set of chromosomes.

What does diploid (2n) mean?

Having two sets of chromosomes.

What does the gametophyte produce?

Gametes (sperm and eggs).

What does the sporophyte produce?

Haploid spores through meiosis.

How does fertilization affect chromosome number?

It combines two haploid gametes to form a diploid zygote.

What are microspores and megaspores?

Microspores develop into male gametophytes;  Megaspore at develops into a female gametophyte.

What is a perfect flower?

A flower with both male and female reproductive parts.

What is a monoecious plant?

A plant with separate male and female flowers on the same plant.

What is a dioecious plant?

A species with male and female flowers on separate plants.

What are the androecium and gynoecium?

The androecium is the male reproductive part; The gynoecieum is the female reproductive part of a flower.

What are the parts of a stamen?

Anther and filament.

What are the parts of a carpel?

Stigma, style, and ovary.

What are the functions of the anther and stigma?

The anther produces pollen; the stigma receives pollen.

What are the functions of the style and ovary?

The style provides a pathway for pollen tube growth;  the ovary contains ovules.

What are the functions of petals and sepals?

Petals often attract pollinators; sepals protect the flower bud.

What is a pollen grain?

The structure containing the male gametophyte.

What are the two main cell types in a developing pollen grain?

Tube cell and generative cell.

What does the generative cell produce?

Two sperm cells through mitosis.

What are the intine and exine?

The inner and outer layers of the pollen grain wall, respectively.

What is pollination?

Transfer of pollen from an anther to a stigma.

What happens when pollen lands on a compatible stigma?

It germinates and grows a pollen tube through the style.

What is the function of the pollen tube?

It transports sperm to the ovule.

What is the micropyle?

An opening in the ovule through which the pollen tube enters.

What is an embryo sac?

The female gametophyte inside an angiosperm ovule.

What cells and nuclei are found in a typical embryo sac?

One egg, two synergids, three antipodals, and a central cell with two polar nuclei.

What is double fertilization?

Two sperm participate in separate fertilization events in the embryo sac.

What does the first sperm fertilize?

The egg, forming a diploid zygote.

What does the second sperm fuse with?

The two polar nuclei, forming a typically triploid endosperm nucleus.

What are the products of double fertilization?

A diploid zygote and typically triploid endosperm.

What is the function of endosperm?

It provides nutrients for the developing embryo.

What does the ovule become after fertilization?

A seed.

What are the main parts of a seed?

Seed coat, embryo, and food supply.

What are cotyledons?

Embryonic seed leaves that may store or absorb nutrients.

What are the radicle, epicotyl, and hypocotyl?

The embryonic root, shoot region above the cotyledons, and stem region below the cotyledons, respectively.

What is a fruit?

A mature ovary and associated accessory parts containing seeds.

What is the main function of fruit?

Protecting seeds and helping disperse them.

What is a dehiscent fruit?

A dry fruit that opens at maturity to release seeds.

What are examples of dehiscent fruits?

Capsules(wheat), legumes(peas), and follicles.

What is an indehiscent fruit?

A dry fruit that does not open at maturity.

What are examples of indehiscent fruits?

Achenes(dandelion), samaras(maple), grains(corn), and nuts.

What are examples of fleshy fruit types?

Berries, pepos, drupes, hesperidia, and pomes.

What are examples of berry, pepo, drupe, hesperidium, and pome fruits?

Tomato, cucumber, cherry, orange, and apple, respectively.

What is the difference between simple, aggregate, and multiple fruits?

Simple: one pistil; aggregate: multiple pistils in one flower(raspberry); multiple: an entire inflorescence(pineapple).

What are common mechanisms of seed dispersal?

Wind, water, animals, and other physical mechanisms.

What is asexual reproduction in plants?

Reproduction without fertilization that can produce genetically similar offspring.

What is vegetative propagation?

Asexual reproduction using plant structures such as stems, roots, or leaves.

What are stolons and tubers?

Stolons are horizontal stems that can form new plants; tubers, such as potatoes, can sprout new shoots.

What are grafting, layering, and micropropagation?

Grafting joins plant parts; layering: stem grow new roots while still attached to the parent plant; micropropagation grows genetically identical clones of a plant

What is the general sequence of sexual reproduction in flowering plants?

Flowering, pollination, fertilization, seed formation, and fruit development.

Why do plants need mineral nutrients?

They are essential for plant cell structure and function.

What are the three nutrients emphasized in commercial fertilizers?

Nitrogen (N), phosphorus (P), and potassium (K).

What are the roles of nitrogen, phosphorus, and potassium?

Nitrogen supports DNA, RNA, proteins, and chlorophyll; phosphorus is part of DNA, RNA, ATP, and membrane phospholipids; potassium supports enzyme function and turgor

Where do plants obtain most of their water and minerals?

From the soil, especially the upper layers.

How do plants absorb water and transport it to leaves?

Root hairs absorb water, which moves upward through the xylem.

How is rock broken down into soil particles?

Freezing water, chemical breakdown, and plant root penetration.

What are the particle-size ranges of sand, silt, and clay?

Sand: 2-0.02 mm; silt: 0.02–0.002 mm; clay: less than 0.002 mm.

What is the approximate composition of soil shown in the presentation?

45% inorganic mineral matter, 25% water, 25% air, and 5% organic matter.

What are soil horizons?

Distinct layers of soil.

What are the A, B, and C horizons?

 A: topsoil with minerals, organisms, and humus; B: less organic matter; C: partially broken-down rock.

What is humus?

Decaying organic material in soil.

Which organisms commonly live in topsoil?

Bacteria, fungi, algae, protists, insects, earthworms, nematodes, and plant roots.

How does repeated cultivation affect soil?

It depletes nutrients and can reduce crop yields.

What is fertilization in agriculture?

Adding mineral nutrients to soil.

How can agriculture negatively affect soil?

It depletes minerals and water reserves and increases erosion.

What caused widespread erosion during the American Dust Bowl?

Soil mismanagement and drought during the 1930s.

What is sustainable agriculture?

No-till farming, cover crops, and crop rotation help?

How do no-till farming, cover crops, and crop rotation help?

They protect soil, reduce erosion, and help break pest cycles.

How do compost, manure, and contour farming support soil conservation?

Compost and manure add organic matter and nutrients

What proportion of global freshwater use goes to agriculture, according to the presentation?

About 75%.

What are aquifers, and what can happen when they are depleted?

Underground water reserves;  land subsidence(sinking)

What is drip irrigation?

Delivering water directly to soil near plant roots.

Why does repeated harvesting deplete soil nutrients?

Nutrients are removed from the field in harvested plant material.

What are organic and inorganic fertilizers?

Organic fertilizers come from plant or animal materials; inorganic fertilizers supply mineral nutrients in inorganic or manufactured forms.

How can fertilizer runoff harm aquatic ecosystems?

Excess nutrients cause algal blooms that can deplete oxygen and kill fish.

What percentage of plant fresh mass is water?

About 80–90%.

What accounts for about 96% of plant dry mass?

Carbon dioxide incorporated into carbohydrates during photosynthesis.

What accounts for about 4% of plant dry mass?

Inorganic substances obtained from soil.

What is an essential plant element?

An element required for a plant to complete its life cycle and reproduce.

How many essential elements are listed in the presentation?

17.

What are macronutrients and micronutrients?

Macronutrients are required in large amounts; micronutrients are required in very small amounts.

What are the nine macronutrients listed?

Carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.

What micronutrients are listed in the presentation?

Iron, manganese, boron, molybdenum, copper, zinc, chlorine, and nickel.

What are common signs of plant nutrient deficiency?

Abnormal leaf coloration, yellowing, discoloration, and tissue damage.

What leaf symptoms are illustrated for nitrogen, phosphorus, and potassium deficiency?

Nitrogen: yellowing; phosphorus: purplish discoloration; potassium: browning or damage at leaf tips and edges

What are mycorrhizae?

Symbiotic associations between plant roots and fungi.

What do plants and mycorrhizal fungi exchange?

Plants provide carbohydrates; fungi improve plant uptake of water and minerals.

What are ectomycorrhizae?

Associations in which fungal mycelium forms a mantle around roots and hyphae grow between root cells without entering them.

What are arbuscular mycorrhizae?

Associations in which fungal hyphae enter the root cortex and penetrate cell walls but not plasma membranes.

What are arbuscules?

Branched fungal structures involved in nutrient transfer.

Approximately how common are ectomycorrhizae and arbuscular mycorrhizae in the presentation?

Ectomycorrhizae occur in about 10% of plant families; arbuscular mycorrhizae occur in about 85% of plant species.

Why is nitrogen important for plant growth?

It is needed in large amounts to produce proteins and nucleic acids.

Which nitrogen forms can plants absorb?

Nitrate (NO₃⁻) and ammonium (NH₄⁺).

What is nitrification?

Bacterial conversion of ammonia to nitrite and then nitrate.

What are ammonification and denitrification?

Ammonification converts organic nitrogen into ammonia or ammonium; ; denitrification converts nitrate into gaseous nitrogen compounds.

What are nitrogen-fixing bacteria?

Bacteria that convert atmospheric nitrogen into biologically usable nitrogen compounds.

What are Rhizobium and root nodules?

Rhizobium are nitrogen-fixing bacteria; root nodules are root swellings containing these bacteria.

What do plants and Rhizobium exchange in root nodules?

Plants receive fixed nitrogen

What is an epiphyte?

A plant growing on another plant that obtains water and minerals from rain.

What is a parasitic plant?

A plant that obtains water, minerals, and sugars from a living host.