KEY CONCEPT All plants alternate between two phases in their life cycles.

Plant life cycles alternate between producing spores and gametes. A two-phase life cycle is called alternation of generations. haploid phase diploid phase alternates between the two fertilization meiosis SPOROPHYTE PHASE GAMETOPHYTE

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

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) gametophyte (1n) capsule spores (1n)

The sporophyte is the dominant phase for seedless vascular plants. Fern spores form in sacs, sori, on underside of mature sporophytes (fronds). sporophyte (2n) sori

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.

Moss life cycle

Fern Life Cycle Fern – (pterophyta) – vascular & nonseed

Conifer Life Cycle Conifers (coniferophyta) – vascular w/ naked seeds

Flowering Plant Life Cycle

KEY CONCEPT Reproduction of flowering plants takes place within flowers.

Flowers contain reproductive organs protected by specialized leaves. Sepals and petals are modified leaves. Sepals are outermost layer that protects developing flower sepal

Petals can help to attract animal pollinators

A stamen is the male structure of the flower. filament anther anther produces pollen grains filament supports the anther

The innermost layer of a flower is the female carpel. style stigma ovary stigma is sticky tip style is tube leading from stigma to ovary ovary produces female gametophyte

Flower Parts

Complete and Perfect Flower Monocot Flower Complete & perfect

Incomplete and Imperfect Flower Dicot Flower

Incomplete and Imperfect Flower Dicot Flower

Complete and Perfect Flower Monocot Flower

Simple fruit simple

Aggregate fruit Aggregate

Multiple fruit multiple

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 in anthers by meiosis each spore divides by mitosis to form two haploid cells two cells form a single pollen grain 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

Pollination occurs when a pollen grain lands on a stigma. pollen tube sperm stigma one cell from pollen grain forms pollen tube other cell forms two sperm that travel down tube

Flowering plants go through the process of double fertilization. female gametophyte ovule egg sperm polar nuclei

Flowering plants go through the process of double fertilization. endosperm seed coat embryo 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.

KEY CONCEPT Seeds disperse and begin to grow when conditions are favorable.

Animals, wind, and water can spread seeds. Seeds dispersed by animals can have nutritious fruits or fruits that cling.

Seeds dispersed by wind can have wing- or parachute- like fruits. Cypselae Double samaras

Seeds dispersed by water can have fruits that float.

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.

KEY CONCEPT Plants can produce genetic clones of themselves through asexual reproduction.

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 leaves or stems may grow new roots grafting joins the parts of two plants together to form a hybrid plant

KEY CONCEPT Plant hormones guide plant growth and development.

Plant hormones regulate plant functions. Hormones are chemical messengers. produced in one part of an organism stimulates or suppresses activity in another part

Gibberellins are plant hormones that produce dramatic increases in size. ending seed dormancy rapid growth of young seedlings rapid growth of some flower stalks

Ethylene causes the ripening of fruits. some fruits picked before they are ripe sprayed with ethylene to ripen when reach destination

Cytokinins stimulate cytokinesis. final stage in cell division produced in growing roots, seeds, and fruits involved in growth of side branches

Auxins lengthen plant cells in the growing tip. stimulates growth of primary stem controls some forms of tropism A tropism is the movement of plant in response to an environmental stimulus.

Plants can respond to light, touch, gravity, and seasonal changes. Phototropism is the tendency of a plant to grow toward light. auxins build up on shaded side of stem cells on shaded side lengthen causes stem to bend toward light

Thigmotropism is a plant’s response to touchlike stimuli. climbing plants and vines plants that grow in direction of constant wind

Gravitropism is a plant’s response to Earth’s gravitational pull. positive gravitropism is downward growth (roots) negative gravitropism is upward growth (shoots)

Some plants have rapid responses not involving growth. Some responses protect plants from predators. Some responses allow plants to capture food.

Photoperiodism is a response to the changing lengths of day and night. triggers some plants to flower triggers fall colors/winter dormancy of deciduous trees