BIOL 1108 EXAM II PDF

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Dr. Susan Z. Herrick BIOL 1108 Unit II Exam Study Guide March 26, 2018 Chapter 29: Plant Structure and Function Pg 599 - The biggest danger associated with moving onto land was the risk of drying out. Desiccation → Excessive water loss

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All land plants are descendents of green algae. Two types of land plants. - Vascular plants: Can pull water from the soil, 95% of plant species. - Bryophytes: Cannot pull water from soil, they exhibit desiccation tolerance ( ability to survive severe dehydration) - That’s why you can find them on rocks and walls, because they don’t need root to penetrate soil. Basic plant anatomy:

Relationship between water and CO2 Less than 1% of the water required for plant survival is designated to its role as an electron donor. - The difference in CO2 concentration on the outside and inside of the leaf effects gas uptake (diffusion down a concentration gradient) as well as the rate of photosynthesis and therefore amount of water required for the plant’s processes. - Water diffuses out of the leaf (transpiration) faster than CO2 does. Role of the waxy cuticle: - Inhibits water loss, but also restricts CO2 intake at the same time. - Small pore (stomata) in the epidermis allows CO2 to come and go easier. Notes on the stomata:

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They allow plants to regulate water loss and carbon dioxide gain. An increase in solute concentration causes water to flow into the cell (osmosis). When solutes leave the guard cells, concentration decreases and water diffuses out of the guard cell, this causes the guard cell to shrink and therefore closing the stomata. Light stimulates the stomata to open.

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The stomata closes when the amount of CO2 inside exceeds that of the outside. (supply is greater than the demand.) - Long story short: Stomata open when condition for photosynthesis are favorable and close when they’re at risk of dehydration. CAM (crassulacean acid metabolism) Plants use CO2 storage to avoid water loss during the day: - CAM plants are usually found in hot and dry e nvironments. - They open their stomata at night, therefore they can uptake a lot of CO2 without losing too much water to evaporation. - CO2 :H2O , 1:50 - CAM plants conserve CO2 by merging CO2 with PEP (phosphoenolpyruvate) via PEP carboxylase then storing it. Water conservation is important for CAM plants and epiphytes (plants that grow on the branches of other plants) Difference between CAM and C4: In CAM plants, CO2 capture and the Calvin cycle take place at different times, while in C4 plants, they take place in different cells. Photorespiration: A more energy expensive alternative to photosynthesis. - When O2 is used a substrate of rubisco. - This produces less ATP in the absence of CO2. - Selectivity of rubisco for CO2 over O2 is reduced as temperature increases. Bundle sheath: A cylinder of cells that surround each vein.

Phloem → Transports carbohydrates from leaves to plant body. (outer tissue) Xylem → Transports water from roots to leaves. (inner tissue) - The structure of xylem makes transporting water much easier because the cells in the walls don’t have cytoplasm or membranes which makes them “hollow.” - Walls have ligin: increases strength and decreased permeability. - Water enters through “pits.” They allow water to pass but not air.

- Water flows faster through longer conduits. There two types of xylem conduits: Tracheids: found in lycophytes, ferns and horsetails, and most gymnosperms. Vessels: Angiosperms. Transpiration:

Risks associated with transpiration: - Collapse: Pulling up too hard can result in the walls to pinch inward, like if you were to usck on a straw too hard. - Cavitation: Abrupt replacement of water by water vapour. - Risks of cavitation is what is prevents angiosperms from living in really cold climates because they have wide xylem. When the conduit freezes and thaws it can cause air bubbles to appear in the xylem. PHLOEM: - Sources: Places that produce the carbohydrates. - Sinks: places that need them to fuel growth and respiration. - Phloem is made of living cells unlike xylem.

- Angiosperms have sieve tubes. - Materials are shuttled by the concentration gradient. - Reproductive region of the plant has priority in terms of where the sugar goes. , - Phloem also provides the rhizosphere with sugars to facilitate the growth of soil microbes. Cell types in phloem: - Sieve tube members - Companion cells - Parenchyma cells - Fibers.

Risks associated with phloem: - Damage from bug due to high sugar content - Damage from high turgor pressure (remember they aren’t ligated like xylem is) Root Anatomy:

Nutrient uptake by the roots is highly selective: Casparian strip: hydrophobic strip which prevents flow of water. Fungi aiding nutrient uptake: Mycorrhizae: S  ymbioses between root and fungus.

-Nitrogen is the nutrient that plants need the most of. Nitrogen fixation: Transforming N2 to more usable forms like ammonia. This is performed by certain bacteria.

Chapter 30: Plant Reproduction Pg 619  uring the life cycle of land plants in one generation the release sperm into a Alternation of Generations: D moist environment and the following generation disperses offspring through the air. Therefore making a pattern of alternating haploid and diploid generations. This evolved so that fertilization could still happen in water while dispersing offspring on land.

Coleochaete a nd Chara → T  wo green algae that are closely related to land plants. - They have a multicellular body. - Entirely haploid (n) cells. - Gametes are formed by mitosis. Coleochaete: h aploid products disperse by swimming with their flagella through water. Chara: Z  ygotes are carried by water currents.

Bryophytes (non-vascular) rely on water as a medium for sperm to swim and therefore for reproduction. - In bryophyte reproduction, the sperm lands on the egg and the young sporophyte develops on the initial female gametophyte. Sporophyte: Is a diploid generation, but produces haploid spores. Gametophyte: Is a haploid generation and produces haploid gametes. - The generations alternate between these two (alternation of generations) The capsule on top of the sporophyte is called the sporangium. - This is where meiosis is happening to make spores. To negate the risk of water washing away the spores, bryophytes usually release their spores when its dry. Sporopollenin: C  oats the spores to protect them from environmental stressors like UV radiation and desiccation. Vascular Plants: - Reproduction is different from that of bryophytes because both the gametophyte and the sporophyte generation is able to supply its own nourishment. Dispersal: - It is vital for ensuring that plants will not need to compete with each other. - It is also important in avoiding pathogens and parasites.

- In ferns the sperm still swim through a film of water. Seed plants eliminated the need for swimming sperm. There are two groups of seed plants: Gymnosperms (conifers and pine) and Angiosperms (flowering plants, they have fruit too) - They can fertilize in dry conditions. - They produce pollen grains.

← pine life cycle

Four steps of seed plant reproduction: 1. Formation of two kinds of spore in separate sporangia. One will develop into the male gametophyte and the other into female. 2. Gametophytes develop within their sporangium and thus remain attached to the sporophyte. Within each sporangium, only a single haploid spore develops into a female gametophyte. a. The ovule is composed of the gametophyte, sporangium and protective layers. The male gametophyte also stays attached to the sporophyte. Many haploid spores are made in the sporangium. b. Pollen is the multicellular male gametophyte along with the sporopollenin. 3. Pollination:  Shedding the pollen, then it is transported by air or animal. a. The male gametophyte must germinate and grow a pollen tube in the tissues of the ovule in order to deliver the gametes to the egg. They are attracted by chemical signals. Fertilization in seed plants takes place without the male gametes needing to be exposed to the external environment.  he seed consists of the 4. After fertilization t he zygote and subsequent embryo form a seed. T embryo, stored resources and an outer protective coat. a. The larger size of the seed allows transport of more resources that can fuel the growth of the offspring, which increases the probability of survival. Example of Seed Plant (Pines): - What we think is “the plant” in all vascular plants, is the sporophyte. - Pines develop two types of cones:  ocated in the upper branches and produce spores that develop into female - Ovule Cones: L gametophytes.  lusters near the tips of branches lower in the tree. Produce spores that - Pollen Cones: C develop into male gametophyte. - Pollen cones are compact shoots with modified leaves that produce sporangia on their surface. Seed plants cont.

The seed is a collection of generations. The seed coat is formed from tissue that surrounded the sporangium, a product of the diploid sporophyte. The center is the embryo: represents the next sporophyte generation.

Modifications that help seeds get around: - Pine seeds developed “wings” that increase their dispersal distance from the parent plant. - Many seeds have seed coats that won’t be affected by digestion as they rely on being passed through an animal's digestive system. Dormancy: The ability for a seed to delay germination. Everything up that point was a seeded plant that does not flower ^^^ Flowering Plants: - They developed animal pollination. The animals serve as “letter carriers.” The part we recognize as the “flower” is the reproductive shoot. - In angiosperms, pollen and ovules are produced in a single structure (the flower)

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To reach the ovules, pollen must land on the stigma, then grown down down in a stalk like fashion. - The role of petals is to attract and orient animal pollinators. - Animal gain from this exchange in the reception of food. Some angiosperm species are self-compatible meaning that they can make viable offspring with their own two kinds of gametes.

Double fertilization: One sperm fuses with the egg to make a zygote. Another sperm fuses with the diploid cell of the female gametophyte, leading to the formation of triploid endosperm. - The endosperm provides nourishment for embryo (from the first sperm). -

Fruits enhancing the dispersal of seeds: - As the fertilized egg develops to form an embryo and the endosperm proliferates around it, the ovary walls develops into a fruit. - Fruits protect immature seeds, as well as serving as something for the animals to eat and dispose of when the seeds are mature.

Asexual Reproduction: - The disperse without the use of seeds. - Apomixis: Synthesis of seeds in the absence of fertilization. - Formation of seeds from diploid cells. The plants made through this are genetically identical their parent plant.

Chapter 31: Plant Growth and Development Pg 641 How vascular plants build their bodies.

Cells with the potential to become one of many cells types is termed “totipotent.” In plants, these totipotent cells are called meristems. Stem growth: The shoot apical meristem is a group of totipotent cells that, like embryonic stem cells in animals gives rise to new tissue. - As new cells are added near the shoot tip, cells that are farther away from the shoot tip cease to divide. - Meristem identity gene: T  he gene the enables cells to have the ability to divide. - Most stem elongation happens at the internodes. - Branches form when the shoot apical meristem divides in two, giving rise to two stems, each with its own shoot apical meristem. - In seed plants, branches form from axillary buds.  (meristems at the base of each leaf) - Dormant until triggered Leaf growth: Leaves begin as small bumps called primordia. Bud scales protect the shoot apical meristem from water loss and damage due to the cold. (They don’t look like leaves but they are formed from the primordia. - While the leaf is developing, files of cells within the leaf begin to elongate, forming discrete strands of procambial cells. - These cells give rise to xylem and phloem. - The region inside the ring of vascular bundles is known as the pith.

- The organization of the vascular bundles provide structure and support to the leaf. Flower growth: Flower development terminates the growth of shoot meristems. - Flowers develop from floral meristems formed by the conversion of shoot meristems. - Floral meristems lose the capacity for continued growth because the cells differentiate. - Whorl: like a layer of the flower. Plant hormones: Hormones affect the growth and differentiation of plant cells. - Growth: irreversible increase in size - Development: formation of new tissues and organs. Five major plant hormones: - Auxin - Gibberellic acid - Cytokinins - Ethylene: fruit ripening and slows root and stem elongation. - Abscisic acid

Polar transport of auxin guides the placement of leaf primordia and the development of vascular connections with the stem. - Auxin causes the shoot to elongate, it also influences the spacing and placement of the leaf primordia. Last function is that it also plays a role in the formation of the vascular bundles. - Polar transport: C  oordinated movement of auxin across many cells in a single division.

Gibberellic acid: Produced in growing regions of the plant (leaves and elongation zones on the stem). It facilitates elongation by reducing the force needed to cause the cell walls to expand. Cytokinins, in combination with other hormones, control the outgrowth of axillary buds. - Avoids overlap - They are produced in meristems. Apical dominance: s uppressing the growth of an axillary bud → due to chemical signals from the shoot tip. Auxin suppresses the growth of axillary buds by inhibiting the synthesis of cytokinins. Secondary growth: - Primary growth is increasing height and secondary growth is increasing diameter. - Plants that have secondary growth are often referred to as “woody.” Lateral meristems: f orm along the length of the stem. They surround the stem. They are active when elongation is complete.  ne kind of lateral meristem. It is the source of new xylem and phloem. Vascular cambium: O  enews and maintains the protective outer layer. Cork cambium:R

The vascular cambium produces secondary xylem and phloem. - It produces new cells that differentiate on both sides. - Inside the vascular cambium becomes secondary xylem and outside is secondary phloem. In old trees the active xylem is located in the sapwood layer. The heartwood at the centre, does not conduct water.

Root growth:

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Roots grow by producing new cells at their tips (root apical meristem). They start to differentiate after elongation is done.

Environmental context on growth and development: - Tropism: the bending or turning of an organism in response to an external signal such as light or gravity. - Stems are positively phototropic → they bend towards the light. - Stems are negatively gravitropic → they grow upward, against gravity. Specialized gravity sensing cells in the root cap contain large starch filled organelles known as statoliths. Seeds are delay germination if they detect the presence of plants overhead. - Phytochromes: photoreceptor that switches back and forth between two stable forms depending on its exposure to light....