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

1. KEY CONCEPTAll plants alternate between two phases in their life cycles.

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

3. sporophyte phase is diploid begins with fertilized egg spores produced through meiosis The gamete-producing plant is the mature gametophyte. • The spore-producing plant is the mature sporophyte. • gametophyte phase is haploid • begins with spore • gametes produced through mitosis

4. Nonvascular plants have a dominant gametophyte phase. moss gametophytes look like green carpet moss sporophytes shoot up as stalklike structures sporophyte (2n) capsule spores (1n) gametophyte (1n) Life cycle phases look different among various plant groups.

5. 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).

6. A fern gametophyte, or prothallus, produces sperm and eggs. gametophyte (1n)) rhizoid • A zygote forms on the prothallus, growing into the sporophyte.

7. 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.

8. The sporophyte is the dominant phase for seed plants.

9. KEY CONCEPTReproduction of flowering plants takes place within flowers.

10. Sepals and petals are modified leaves. Sepals are outermostlayer that protectsdeveloping flower sepal Flowers contain reproductive organs protected by specialized leaves.

11. petal • Petals can help to attract animal pollinators

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

13. 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

14. Flowering plants pollinated when pollen grains land on stigma. Wind pollinated flowers have small flowers and large amounts of pollen. Flowering plants can be pollinated by wind or animals.

15. many flowering plants pollinated by animal pollinators Animal pollinated flowers have larger flowers and less pollen. pollen grains • pollination occurs as animal feeds from flower to flower • animal pollination more efficient than wind pollination

16. 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 pollen grain

17. 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 One female gametophyte can form in each ovule of a flower’s ovary.

18. 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

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

20. 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

21. Each ovule becomes a seed. The surrounding ovary grows into a fruit.

22. KEY CONCEPTSeeds disperse and begin to grow when conditions are favorable.

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

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

25. Seeds dispersed by water can have fruits that float.

26. Seed dormancy is a state in which the embryo has stopped growing. Seeds begin to grow when environmental conditions are favorable. • Dormancy may end when conditions are favorable. • While dormant, embryo can withstand extreme conditions.

27. 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

28. 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

29. 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

30. Once photosynthesis begins, the plant is called a seedling.

31. KEY CONCEPTPlants can produce genetic clones of themselves through asexual reproduction.

32. 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

33. stems, leaves, or roots attached to parent plant produce new individuals specific adaptations include stolons, rhizomes, and tubers Vegetative reproduction is another type of asexual reproduction.

34. 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

35. KEY CONCEPTPlant hormones guide plant growth and development.

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

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

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

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

40. 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.

41. 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

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

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

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

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