1. Ch. 24- Reproduction of Seed Plants

2.  I. Reproduction With Cones and Flowers  A. Alternation of Generations  - All plants have a life cycle in which a diploid sporophyte generation alternates with a haploid gametophyte generation. Haploid Diploid MEIOSIS FERTILIZATION Gametophyte Plant (N) Sporophyte Plant (2N)

3.  B. Life Cycle of Gymnosperms  - Reproduction in gymnosperms takes place in cones, which are produced by a mature sporophyte plant.  1. Pollen cones  a. Also called male cones.  b. Produces the male gametophytes, which are called pollen grains.

4.  2. Seed Cones  a. Produce female gametophytes  b. Much larger than pollen cones  c. At the base of each cone scale are found 2 ovules in which the female gametophytes develop

5.  3. Pollination – The pollen is carried by the wind and caught on a sticky secretion (pollination drop) on one of the scales of the female cone.

6.  4. Fertilization  a. When a pollen grain lands near an ovule, it grows a pollen tube into the ovule.  b. A sperm from the pollen tube fertilizes the egg in the ovule.

7. 5. Development a. Fertilization produces a zygote which grows into an embryo b. The embryo becomes enclosed in a seed

8. ANGIOSPERM  C. Structure of Flowers  - Flowers are the reproductive organs that are composed of four kinds of specialized leaves: sepals, petals, stamens, and carpels. (Figure 24-5)

9. Filament Anther StyleStigma Ovary Petal Ovule Sepal Stamen Pistil

10.  1. Sepals  a. The outermost circle of floral parts contains the sepals, which in many plants are green and closely resemble ordinary leaves  b. Enclose bud and protect the flower during development

11.  2. Petals  a. Brightly colored and found just inside the sepals  b. Attract insects and other pollinators to the flower

12.  3. Stamens  a. Produce male gametophytes – pollen grains  b. Consists of anther and filament

13.  4. Carpels  a. Also called pistils  b. produce female gametophytes – eggs  c. Consists of ovary, style, and stigma

14.  D. Life Cycle of Angiosperms  1. Reproduction in angiosperms takes place within the flower  2. Following pollination and fertilization, the seeds develop inside protective structures

15.  E. Pollination  1. Most gymnosperms and some angiosperms are wind pollinated, whereas most angiosperms are pollinated by animals.  2. Insect pollination is more efficient than wind pollination, giving insect-pollinated plants a greater chance of reproductive success.

16.  F. Fertilization in Angiosperms  1. Double Fertilization – Inside the embryo sac, two distinct fertilizations take place  a. First, one of the sperm nuclei fuses with the egg nucleus to produce a diploid zygote, which will grow into the new plant embryo.

17.  b. Second, the other sperm nucleus fuses with two polar nuclei in the embryo sac to form a triploid (3N) cell. This will grow into a food-rich tissue know as endosperm, which nourishes the seedling as it grows.

19.  II. Seed Development and Germination  - the development of the seed, which provides protection and nutrition for the embryo, was a major factor in the success of plants on land.

20.  A. Seed and Fruit Development  1. As angiosperm seeds mature, the ovary walls thicken to form a fruit that encloses the developing seed.  2. The term fruit, biologically speaking, applies to any seed that is enclosed within its embryo wall.

23.  http://www.youtube.com/watch?v=zVNs CW6eiiw http://www.youtube.com/watch?v=zVNs CW6eiiw

24.  B. Seed Dispersal  1. Dispersal by Animals- Seeds dispersed by animals are typically contained in fleshy, nutritious fruits.

25.  2. Dispersal by Wind and Water- Seeds dispersed by wind or water are typically light weight, allowing them to be carried in the air or to float to the surface of the water.

27.  C. Seed Dormancy  1. Some seeds sprout rapidly while other seeds enter a period of dormancy, during which the embryo is alive but not growing.  2. Environmental factors such as temperature and moisture can cause a seed to end dormancy and germinate.

28.  D. Seed Germination  - The early growth stage of the plant embryo