Plant Life Cycles

1. Plant Life Cycles Modern Biology Chapter 32

2. Alternation of Generations: the overview

3. Mosses: Structures involved • What you associate with mosses is a gametophyte • Gametophytes are haploid

5. …Because repetition is the spice of life!

6. Mosses: Development/ Growth • Mitosis occurs producing a diploid sporophyte • Sporophyte remains attached to the gametophyte • Diploid • Sporophyte cannot feed itself, but is genetically different than the gametophyte

7. Mosses: The next generation… • Diploid sporophyte produces cells that undergo meiosis; this produces haploid organisms, or gametophytes.

8. Ferns

9. Ferns: Structures involved • What you associate with ferns is the sporophyte • Sporophyte grows from gametophyte • Gametophytes are tiny (10 mm) • Antheridium • Archegonium

11. Ferns: Development/ Growth • Mitosis occurs producing a diploid sporophyte with fronds • Sporophyte remains attached to the gametophyte, crushing it as it increases in size

12. Ferns: The next generation… • Specialized cells, usually on the underside of the fronds, undergo meiosis and produce spores.

13. Conifers

15. Conifers: Fertilization • Typically the conifers much reach maturity before they can reproduce sometimes up to 30 years. • Conifers can reproduce without water for the sperm to swim in. • Sexual reproduction can actually take years

16. Flowering Plant Life Cycles Modern Biology Chapter 32

17. Flowering plants: Structures involved

22. Consists of a mega sporangium surrounded by two integuments Ovule: female sex cell

23. One large diploid megaspore mother cell undergoes meiosis and produces 4 haploid megaspores Ovule: female sex cell

24. One megaspore enlarges and the other three wither away…. Ovule: female sex cell

25. Remaining mega spore undergoes three mitotic divisions to produce 8 haploid nuclei Ovule: female sex cell

26. Two nuclei move to the center of the cell while the remaining 6 move to the polar ends- three to each side Ovule: female sex cell

27. Cell walls form around the 6 nuclei at the ends One of these 6 cells becomes the egg, (the others die at fertilization) Embryo sac consists of 7 cells and 8 nuclei- this is the mature female gametophyte Ovule: female sex cell

29. Microspore mother cells undergo meiosis and produces 4 haploid microspores, each of which undergoes mitosis to form two haploid cells Pollen: male sex cell

30. Wall develops around microspores and the two celled structure is a pollen grain- this is the mature male gametophyte Pollen: male sex cell

31. The larger cell will produce the tube cell containing the tube nucleus. When attached, the tube nucleus will make a pollen tube The smaller cell is the generative cell It will undergo yet another mitotic division to produce two sperm Pollen: male sex cell

32. Pollen tube grows from pollen (takes about a day) Flowering plants: Fertilization (Double Fertilization)

33. The two cells produced from the generative cell enter the ovule through the pollen tube One of the sperm fuses with the egg to form a diploid zygote This will be the embryo Flowering plants: Fertilization (Double Fertilization)

34. The two cells produced from the generative cell enter the ovule through the pollen tube The other sperm fuses with the two nuclei in the megaspore to produce a triploid nucleus. This will be the endosperm- the nutrients contained within a seed so that the embryo has energy to remain alive and begin the growth process Flowering plants: Fertilization (Double Fertilization)

35. Video!!

37. Flowering plants: Seed structure

38. Seeds can remain dormant for many years When the conditions are right, the seed will germinate Flowering plants: Seed germination

39. Typically roots come before leaves Flowering plants: Seed germination

42. Flowering plants: fruit