1. LIFE CYCLES OF PLANTS ABBOTTS COLLEGE ABBOTTS 1

2. TOPICS 2  DEFINITIONS  Alternation of generations  Haploid  diploid  LIFE CYCLES OF:  Moss  A flower  DEFINITIONS  Alternation of generations  Haploid  diploid  LIFE CYCLES OF:  Moss  A flower

3. Asexual and sexual reproduction AsexualSexual Produces genetically identical organisms Produces organisms that are not genetically identical Faster processSlower Replaced damaged cells and tissuesProduces sex cells or gametes Takes place in favourable conditionsTakes place in unfavourable conditions Cells divide by mitosisCells divide by meiosis No sexes involvedMale and female organisms required Asexual reproduction = No sex cells or gametes involved. No sexes male or female organisms required. Sexual reproduction = Sex cells or gametes involved. Male or female organisms required.

4. Sexual reproduction involves the two alternating processes of meiosis and fertilization. In meiosis, the chromosome number is reduced from the diploid to the haploid number.meiosisdiploidhaploid In fertilization, the nuclei of two gametes fuse, raising the chromosome number from haploid to diploid. Whatever variation in details there may be from one organism to another, these two activities must occur alternately if sexual reproduction is to continue. ANIMALS Meiosis generates the haploid gametes — sperm and eggs — directly. These single cells fuse to form the zygote which will develop into another diploid animal.zygote. Alternation of Generations

5. PLANTS Meiosis and fertilization divide the life of the organism into two distinct phases or "generations". The gametophyte generation begins with a spore produced by meiosis. The spore is haploid, and all the cells derived from it (by mitosis) are also haploid. In due course, this multicellular structure produces gametes — by mitosis — and sexual reproduction then produces the diploid sporophyte generation. The sporophyte generation thus starts with a zygote. Its cells contain the diploid number of chromosomes. Eventually, though, certain cells will undergo meiosis, forming spores and starting a new gametophyte generation Alternation of Generations

6. PLANTS ANIMALS

7. Alternation of Generations

8. ALTERNATION OF GENERATIONS 8  All terrestrial plants have two phases in their life cycles:  A haploid gametophyte generation that alternates with a diploid sporophyte generation  All terrestrial plants have two phases in their life cycles:  A haploid gametophyte generation that alternates with a diploid sporophyte generation

9. 9

10. ALTERNATION OF GENERATIONS 10  A haploid spore grows into the haploid gametophyte generation  that produces gametes  A diploid zygote grows into a diploid sporophyte generation  Certain cells undergo meiosis and form halpoid spores  Which are the start of the new gametophyte generation  A haploid spore grows into the haploid gametophyte generation  that produces gametes  A diploid zygote grows into a diploid sporophyte generation  Certain cells undergo meiosis and form halpoid spores  Which are the start of the new gametophyte generation

11. LIFE CYCLE OF A BRYOPHYTE Eg MOSS 11  Shows a clear alternation of generations  Gametophyte is the more prominent phase  The sporophyte is attached to it and dependent on it  Shows a clear alternation of generations  Gametophyte is the more prominent phase  The sporophyte is attached to it and dependent on it DIAGRAM OF THE MOSS LIFE CYCLE

12. Bryophytes Eg. Moss No conducting tissue (no xylem and phloem) No proper roots Gametophyte generation is more prominent Sporophyte dependant on gametophyte 2n n

13. 13

14. 14

15. LIFE CYCLE OF A FLOWERING PLANT 15  Are the dominant terrestrial plants  Shows a clear alternation of generations  Gametophyte is less prominent than the sporophyte  There are separate male and female gametophytes  Both are microscopic with the female gametophyte dependent on the sporophyte  Are the dominant terrestrial plants  Shows a clear alternation of generations  Gametophyte is less prominent than the sporophyte  There are separate male and female gametophytes  Both are microscopic with the female gametophyte dependent on the sporophyte

16. 16

17. 17

18. 18

19. 19

20.  THE END 20