Lecture 6 Flashcards
Describe the aditional challenge posed by the waxy cuticle and how this challenge was solved
Cuticle: a waxy, watertight sealant that covers the above ground parts of plants, and that gives them the ability to survive in dry environments. Problem? • Inhibits the uptake and release of gases! Solution? • Stomata: small openings (pore) surrounded by guard cells in the epidermis of leaves and stems.
Describe the roles of guard cells
As guard cells take on water, they become turgid and their volume expands.
• Expansion does not occur evenly because:
• Inner walls are thicker + less extensible than the outer walls.
• Orientation of cellulose microfibrils expand lengthwise.
• Result: When turgid, guard cells bow outward, opening a pore b/w them.
• When guard cells lose water become less bowed and the pore closes.
• Changes in turgor in guard cells results primarily from reversible absorption and loss of K+
. • K+
is not transported directly; H+ actively pumped out of cell – sets up membrane potential for diffusion of K+
. • Water follows by osmosis.
why early plants had less control over water loss?
Stomata are present in all plants except the liverworts, which have pores, but no guard cells.
The earliest land plants had pores that allowed gas exchange to occur, but no guard cells with which to control gas exchange and thus water loss.
• The presence of guard cells later allowed control over moisture retention, by allowing the organism to selectively open and close these holes.
list several adaptations of xerophytes for reducing water loss
Xerophytes: plants that live in arid environments. • Adaptations include: • CAM/C4 (sweet BIO111 memories…) • Small leaves • No leaves (except after heavy rainfall) • Store water • Extremely long roots • Long white bristles that reflect sunlight • Stomata in pits
State the challenge that was overcome by vascular tissue and why was advantages.
Advantages of vertical growth:
• More access to sunlight, less competition.
Differentiate between xylem and phloem both structurally and functionally.
• Xylem: transports water and minerals from roots to shoots. are dead and hollow at maturity
• Phloem: transports products of photosynthesis(sugars). phloem are
alive at maturity BUT lack nucleus, ribosomes, and
cytoskeletal elements. Enables nutrients to
pass easily through cell.
Briefly describe how vascular tissue evolved
Lignin rings in cell walls of vascular tissue gave stem tissues of early land plants the strength to remain upright.
• Evolved to become stronger and more efficient at transporting water.
tracheids: a type of water-conducting cell in the xylem that lacks perforations in the cell wall
Diagram the Alternation of Generations life cycle and its ploidy
do in notes
Distinguish between spore, gamete and zygote
notes
explain why non-vascular plants are typically found in damp moist conditions
Flagellated sperm
Describe at least 3 adaptations that contributed to the success of seed plants on land and explain the advantage of all these adaptations to the plant
Key innovation 1: Spores that resist drying while
dispersing through air.
• All land plants have spores that are produced within structures called sporangia and that are encased in a tough coat of sporopollenin.
• Protects the spore from drying and from mechanical damage during transport in air.
• If spores reach good habitat for growth, tough walls crack open, and a new gametophyte develops.
Key innovation 2: Evolution of complex, protective,
multicellular structures within which gametes are produced.
• Gametophytes of all land plants (except flowering plants) produce their gametes within gametangia.
• Specialized reproductive organs that protect gametes from drying and from mechanical damage.
• Flowering plants have structures inside the flower that perform the same function.
The sperm producing male gametangium = antheridium.
The female egg-producing gametangium = archegonium
Key innovation 3: Retention and nourishment of the embryo by the mother plant.
• Instead of shedding their eggs into water or soil, land plants retain their eggs – i.e. once fertilized the zygote remains enclosed within the gametophyte tissues.
Zygote sheltered and nourished by the parent plant as it develops into an embryo = a young sporophyte
For this reason, all land plants are known as “embryophytes”
Define: heterospory
Seed plants produce two types of spores: Microspores • Produced in microsporangia • Develop into male gametophytes Megaspores • Produced in megasporangia • Develop into female gametophytes
distinguish between pollination and fertilization
Pollination
• Transfer of pollen to the part of the
seed plant that contains the ovules.
Fertilization
• The union of sperm and egg.
Describe a seed (what is it) and compare it to a spore
A seed = an embryo, a food supply, and
a tough protective coat.
Spore = is a single cell that is capable of developing into an adult organism
and that is not produced by the fusion of gametes.
A chief difference between spores and seeds as dispersal units is that spores have very little stored food resources compared with seeds, and thus require more favorable conditions in order to successfully germinate
describe two adaptations that contribute to the success of flowering plants. and explain the advantages of these adaptations
Flowers: increase probability that an animal will perform pollination, instead of leaving it to chance with wind.
Fruit: To protect and disperse seed
In general terms, explain how the basic plant life with alternation of generations is modified in gymnosperms and angiosperms
Seeds
Describe the following floral organs and their functions:
sepals, pedals, stamen, carpel
Stamens = male reproductive organs.
• Consists of 2 structures:
• Filament: a stalk
• Anther: contains chambers called microsporangia (pollen sacs) that produce pollen.
Carpels = female reproductive organs. • Each carpel has: 1. An ovary at the base. 2. A slender neck called the style, 3. A sticky structure called the stigma at the top of the style that serves as a landing platform for pollen.
Sepals and petals are sterile structures.
• Sepals
• Outermost part of a flower.
• Usually green and more leaf-like in appearance than the other floral
parts.
• Enclose and protect the floral bud before it opens.
• Petals • Often brightly colored. • Advertise the flower to insects and other pollinators. • Specialized cells in petals may produce a scent attractant.
Distinguish between complete and incomplete flowers
Complete flower: has all 4 whorls (i.e., all four basic floral
organs).
Incomplete flower: missing any of the 4 organs.
Distinguish between perfect flower and imperfect flower
Perfect flower: has both stamens and carpels.
Imperfect flower: has either stamens or carpels, but not both.
A complete flower is also perfect, but a perfect flower is not necessarily complete!
Distinguish between monoecious and dioecious
Dioecious species cannot self-pollinate because
different individuals have flowers with either stamens
or carpels.
• Monoecious plants have either perfect flowers, or male and female imperfect flowers on the same individual.
What is the purpose of a flower and why is there so much variation amoung flowers
increase probability that an animal will perform pollination, instead of leaving it to chance with wind.
• Much of floral diversity represents adaptation to specific pollinators.
Define: coevolution and give an example
• Coevolution: joint evolution of two interacting species, each in response to selection imposed by the other. example: • Insect with long tongue, flower with long tube structure.
Explain why flowers are conniving and manipulative
To trick animals into caring their pollen
Contrast the flowers of, the amount of pollen released by, wind versus animal pollenation species
About 80% of angiosperm species rely on animals for pollen transfer; 20% rely on wind; <1% on water.
wind pollenating flowers are not as pretty and have no leaves in the spring to get in the way of wind. also release a lot more pollen because they have less success rate
