Transcript Section 3
Section 3 Seed reproduction pollen • • • • Spores develop in pollen grains Has water resistant covering Male sperm Transfer to female part by wind, gravity, water and animals • Creates pollen tube when reaches female part. Sperm moves thru tube to ovary seeds • Develop after fertilization • Has food source (embryo) and a seed coat for protection • Embryo produces stems, roots, and leaves • New plants develop faster from seeds than spores • Gymnosperms and angiosperms are seed plants. Gymno. produce seeds in cones, angio. in flowers and fruit Gymnosperm reproduction • • • • • Cones are repro. structures Include pines Produce male and female cones Egg is produced in ovule in spring, male cones release clouds of pollen to fertilize female cones Gymnosperm seeds • Pollen falls on female cone and can take 2 to 3 years for seeds to be released Angiosperm reproduction • Most earth plants today are angio. • All have flowers (reproductive organs) • Flowers produce sperm and egg The flower • • • • • Four main parts-petals, sepals, stamen and pistil Colorful parts are petals Sepals cover the bud Stamen is male repro. part Pistil is female part containing swollen ovary at its base • Not all flowers have all 4 parts Importance of flowers • Large, colorful flowers attract insects and other animals. Pollen sticks to them and is moved around • Some plants depend on wind and water to spread pollen Angiosperm seeds • Flower is pollinated when pollen reaches the stigma and a pollen tube forms allowing the pollen to reach the ovule and fertilize the egg • A zygote forms and grows into a plant embryo Seed development • Part of ovule develops into the stored food (cotyledon) and seed coat Seed dispersal • Most seeds grow only when placed in soil • Gravity pulls seeds to ground • Carried great distances by wind, water and animals germination • Events that result in the growth of a plant from a seed • Some germinate and some can stay in resting stage for hundreds of years • Seeds only germinate when conditions are right • Water absorption causes germination • Energy is released from cotyledon and a root grows followed by stems and leaves • Photosynthesis takes over