CHAPTER 3 LESSON 4
-Plants have complex life cycles that include two different stages, the sporophyte
stage and the gametophyte stage
-Sporophyte stage- the plant produces spores or seeds, tiny cells that can grow
into new organisms
-The spore develops into the plant's other stage (gametophyte)
-Gametophyte stage- the plant develops two kinds of cells, sperm cells and egg cells
-Angiosperms are classified based on the length of their life cycle
-Annuals are flowering plants that complete a life cycle within one growing season
(marigolds, petunias, wheat, cucumbers)
-Biennials are angiosperms that complete their life cycle in two years (parsley,
celery, foxglove)
1st year- grow roots, short stems, leaves
2nd year- lengthen their stems, grow new leaves, produce flowers and seeds
-Perennials are flowering plants that live for more than two years
-Most perennials flower every year
-All plants undergo sexual reproduction that involves fertilization
-Fertilization occurs when a sperm cell unites with an egg cell
-A zygote is the fertilized egg
-For algae and some plants fertilization can only happen if water is in the
environment
-Many plants can undergo asexual reproduction
-New plants can grow from the roots, leaves, or stems of a parent plant
-Asexual reproduction does not involve flowers, pollination, or seeds
-Asexual reproduction can occur faster than sexual reproduction
-Asexual reproduction can reproduce unfavorable traits since there is no new
genetic material being passed to offspring
-Scientists can take advantage of asexual reproduction- a single plant can be used
to create identical plants for experiments
-Scientists can copy plants with favorable characteristics
-Grafting is a way to copy plants- part of a plants stem is cut and attached to
another related plant species (orange and lemon). When the plant matures it can
produce more than one type of fruit
-Mosses, liverworts, hornworts, ferns, club mosses, and horsetails need to grow in
moist environments
-These plants release spores into their surroundings (they grow into gametophytes)
-Gametophytes produce egg and sperm cells
-Water must be available so the sperm can swim toward the eggs
-Gymnosperm Reproduction:
1.Cone Production:
-Most gymnosperms have reproductive cells called cones
-Cones are covered in scales
-Most gymnosperms (a single plant) produce male and female cones
-In some gymnosperm plants, individual trees either grow male or female
cones (not both)
-Some gymnosperms produce no cones
2. Pollen Production and Ovule Development
-Male cones produce pollen
-The female gametophyte develops into structures called ovules
-An ovule is a structure that contains an egg cell
-Female cones contain at least one ovule at the base of each scale
-Ovules develop into seeds
3. Egg Production:
-Two egg cells form inside each ovule on the female cone
4. Pollination:
-Transfer of pollen from male to female reproductive structure
-Wind carries pollen
-Pollen collects on a sticky substance made by the ovules
5. Fertilization:
-After pollination, the ovule closes and seals in the pollen
-Scales close
-Sperm cell fertilizes egg cell inside each ovule
-Zygote develops into the embryo part of the seed
6. Seed Development:
-Female cones remain on tree while seed matures
-Female cone gets bigger
-It can take up to two years for seeds to mature
-Male cones fall off the tree once they have shed their pollen
7. Seed Dispersal:
-When seeds are mature the scales open
-Wind shakes seed out of cone and carries them away
-Angiosperm Reproduction:
1. Pollination:
-Flowers are pollinated when a grain of pollen falls on the stigma
-Animals and wind help the pollination process
2. Fertilization:
-Pollen falls on the stigma
-Sperm cell joins with egg cell inside the ovule (inside the ovary)
-Zygote develops into the seed's embryo
-Other parts of the ovule develop into the rest of the seed
3. Fruit Development and Seed Dispersal
-Ovary turns into a fruit- The ripened ovary
-One or more seeds are in the fruit
-Apples, cherries, tomatoes, squash
-Animals eat fruit help disperse their seeds by
depositing them in new areas