KEY CONCEPTAll plants alternate between two phases in their life cycles.
SPOROPHYTE PHASE fertilization meiosis GAMETOPHYTE PHASE Plant life cycles alternate between producing spores and gametes. A two-phase life cycle is called alternation of generations. haploid phase diploid phase alternates betweenthe two
The spore-producing plant is the mature sporophyte. sporophyte phase is diploid begins with fertilized egg spores produced through meiosis The gamete-producing plant is the mature gametophyte.
gametophyte phase is haploid
begins with spore
gametes produced through mitosis
sporophyte (2n) capsule spores (1n) gametophyte (1n) Life cycle phases look different among various plant groups. Nonvascular plants have a dominant gametophyte phase. moss gametophytes look like green carpet moss sporophytes shoot up as stalklike structures
sporophyte (2n) sori The sporophyte is the dominant phase for seedless vascular plants.
Fern spores form in sacs, sori, on underside of mature sporophytes (fronds).
A fern gametophyte, or prothallus, produces sperm and eggs. gametophyte (1n)) rhizoid
A zygote forms on the prothallus, growing into the sporophyte.
The sporophyte is the dominant phase for seed plants. pine trees are typical seed plant sporophytes female spores produced in female cones male spores produced in male cones male spores develop into pollen grains, the male gametophytes female spores develop into female gametophytes that produce eggs sperm from pollen travel down pollen tube toward egg fertilized egg develops into embryo ovule develops into protective pine seed
The sporophyte is the dominant phase for seed plants.
sepal Flowers contain reproductive organs protected by specialized leaves. Sepals and petals are modified leaves. Sepals are outermostlayer that protectsdeveloping flower
petal Petals can help to attract animal pollinators
stamen filament anther A stamen is the male structure of the flower.
anther produces pollen grains
filament supports the anther
stigma style carpel ovary The innermost layer of a flower is the female carpel.
stigma is sticky tip
style is tube leading from stigma to ovary
ovary produces female gametophyte
Flowering plants can be pollinated by wind or animals. Flowering plants pollinated when pollen grains land on stigma. Wind pollinated flowers have small flowers and large amounts of pollen.
Animal pollinated flowers have larger flowers and less pollen.
many flowering plants pollinated by animal pollinators pollen grains
pollination occurs as animal feeds from flower to flower
animal pollination more efficient than wind pollination
Fertilization takes place within the flower.
Male gametophytes, or pollen grains, are produced in the anthers.
male spores produced inanthers by meiosis
each spore divides bymitosis to form twohaploid cells
two cells form asingle pollen grain
One female gametophyte can form in each ovule of a flower’s ovary.
four female spores produced in ovule by meiosis one spore develops into female gametophyte female gametophyte contains seven cells one cell has two nuclei, or polar nuclei one cell will develop into an egg
pollen tube sperm stigma Pollination occurs when a pollen grain lands on a stigma.
one cell from pollen grain forms pollen tube
other cell forms two sperm that travel down tube
female gametophyte egg sperm polar nuclei ovule Flowering plants go through the process of double fertilization.
endosperm seed coat embryo
Flowering plants go through the process of double fertilization.
one sperm fertilizes the egg
other sperm unites with polar nuclei, forming endosperm
endosperm provides food supply for embryo
Each ovule becomes a seed.
The surrounding ovary grows into a fruit.
Animals, wind, and water can spread seeds.
Seeds dispersed by animals can have nutritious fruits or fruits that cling.
Cypselae Double samaras
Seeds dispersed by wind can have wing- or parachute-like fruits.
Seeds begin to grow when environmental conditions are favorable. Seed dormancy is a state in which the embryo has stopped growing.
Dormancy may end when conditions are favorable.
While dormant, embryo can withstand extreme conditions.
Germination begins the growth of an embryo into a seedling.
water causes seed to swell and crack coat
embryonic root, radicle, is first to emerge
water activates enzymes that help send sugars to embryo
Germination begins the growth of an embryo into a seedling. water causes seed to swell and crack coat embryonic root, radicle, is first to emerge water activates enzymes that help send sugars to embryo
embryonic shoot, plumule, emerges next
Germination begins the growth of an embryo into a seedling. water causes seed to swell and crack coat embryonic root, radicle, is first to emerge water activates enzymes that help send sugars to embryo embryonic shoot, plumule, emerges next
leaves emerge last
Once photosynthesis begins, the plant is called a seedling.
Plants can reproduce asexually with stems, leaves, or roots. Asexual reproduction allows a plant to make copies of itself. Regeneration is one type of asexual reproduction. plants grow a new individual from fragment of parent occurs when piece of a stem, leaf, or root falls off parent plant
Vegetative reproduction is another type of asexual reproduction.
stems, leaves, or roots attached to parent plant produce new individuals specific adaptations include stolons, rhizomes, and tubers
Humans can produce plants with desirable traits using vegetative structures. Vegetative propagation takes advantage of plants’ ability to reproduce asexually. Humans use one plant with desirable traits to produce many individuals.
cutting of leavesor stems may grow new roots
grafting joins the parts of two plants together to form a hybrid plant