Download - Creating the next generation
Creating the next generation
Plant Reproduction Creating the next generation Asexual
Reproduction Asexual reproduction is natural cloning.Parts of the
plant, such as leaves orstems, produce roots and become
anindependent plant. List some benefits and some drawbacksto
asexual reproduction. Fast, no mate required. Beneficial for plants
that must compete for scarce resources. However, all individuals
are genetically identical. Sexual Reproduction Sexual reproduction
requires fusion ofmale cells in the pollen grain with femalecells
in the ovule. List some advantages and drawbacks tosexual
reproduction. Fusion of egg and sperm cells. May be limited to a
certain season. Slower than asexual reproduction. Allows genetic
mixing, increasing variability in a population. Terms to know:
Haploid: having a single set ofchromosomes in each cell. Diploid:
having two sets ofchromosomes in each cell. Mitosis: cell division,
which producestwo genetically identical cells. Meiosis: reduction
division, whichproduces four haploid reproductive cells. Plant Life
Cycle Alternation of Generations
Plants have a double life cycle with twodistinct forms: Sporophyte:
diploid, produce haploidspores by meiosis (reduction division).
Gametophyte: haploid, producegametes by mitosis (simple
celldivision). Non-flowering plants Mosses, ferns, and related
plants havemotile, swimming sperm. What kind of environmental
conditionswould be required for reproduction inthese plants? What
kinds of limits does externalreproduction impose on these plants?
Reproduction in these plants requires wet conditions, and requires
having male and female parts close together. Living conditions,
plant size, and genetic mixing is limited. Moss Life Cycle Fern
Life Cycle Conifers Conifers (also non-flowering plants)
havereduced gametophytes. Male gametophyte is contained in a
drypollen grain. Female gametophyte is a few cellsinside of the
structures that becomethe seed. Conifer life cycle Conifer
pollination Conifers are wind-pollinated plants.
Chance allows some pollen to land onthe scales of female cones.
Pollen germinates, grows a pollen tubeinto the egg to allow sperm
to fertilize theegg. What are some advantages anddisadvantages to
wind pollination? Animals vs. Plants Plant Reproduction Animal
Reproduction Life cycle
Alternation of generations No alternation of generations Gametes
Haploid gametes Spores Haploid spores No spores Gametes made by
Haploid gametophyte, by mitosis Diploid organism, by meiosis Spores
made by Diploid sporophyte, by meiosis Flowers Pollen go-betweens
Showy flowers are the result of selectionfor more efficient
pollination strategies. Flower parts are modified leaves. Thosethat
were brightly colored attractedinsects in search of pollen. Why
would insects search for pollen?What other rewards do flowers
offer? What are advantages and disadvantagesto relying on insects
as pollinators? Pollen itself is a protein-rich food for insects.
Some plants offer other rewards, such as nectar. Flower Parts
Incomplete flowers Flowers are complete if they have allparts, and
perfect if they have both maleand female parts. Grass flowers:
incomplete, usuallyimperfect (separate male and femaleflowers) A
tulip is complete (though the sepalsare the same color as the
petals) andperfect. Imperfect flowers Angiosperm Life Cycle
Gametogenesis: Male Gametogenesis: Female Double Fertilization
Fruits From ovary to fruit The ovary of the flower contains the
ovules.
As fertilized ovules develop into seeds,the ovary wall develops
into the fruit. In science, the term fruit refers to amature ovary
that contains seeds. Flower to Fruit Types of dry fruits Capsule
(Poppy) Legume (Bean pod) Achene
(Sunflower) Follicle (Columbine) Silique (Money Plant) Nut
(Hazelnut) Types of fleshy fruits Drupe (Peach) Pome (Apple) Pepo
(Cucumber)
Berry (Tomato) Aggregate (Strawberry) Multiple (Pineapple) Seeds
Ovule to seed Seed Anatomy Seed anatomy Seed dormancy Seeds can
remain dormant in the soil forlong periods of time. Dormancy
helpsensure that seeds only germinate whenconditions are right.
When we weed or cultivate a bare patchof soil, the weeds that
sprout upimmediately usually come from the seedbank already in the
soil. Breaking dormancy Seeds require moisture and the
righttemperature to germinate. In addition, some seeds germinate
onlyafter certain environmental signals: Drying Temperature (period
of cold or heat) Disruption of the seed coat Seed Germination