Reproduction

Step 1: In asexual reproduction offspring are usually similar to the parent. Step 2: Similarity keeps variation low. Step 3: If one form is weak in a changed environment, the whole population may be at risk.

Step 1: In sexual reproduction two gametes fuse. Step 2: If both have half the number, fusion restores the normal number. Step 3: This keeps chromosome number stable in the species.

Step 1: The nucleus contains genetic information. Step 2: Binary fission forms two new cells. Step 3: If the nucleus does not divide first, information will not be distributed properly.

Step 1: Some microorganisms can form a protected stage in difficult conditions. Step 2: Repeated divisions can occur inside it. Step 3: When conditions become favorable, many offspring can emerge together.

Step 1: In budding, a bud forms on the parent body. Step 2: The bud gradually develops body structures. Step 3: After enough development, it can separate and live independently.

Step 1: In fragmentation the body breaks into pieces that may form new organisms. Step 2: In regeneration lost parts can regrow, and in some organisms a new organism can form. Step 3: Therefore use the two terms carefully.

Step 1: Rhizopus reproduces by spores. Step 2: Spores may have a thick wall. Step 3: This wall protects them in difficult conditions and allows germination when conditions improve.

Step 1: Vegetative propagation can produce plants with traits similar to one parent. Step 2: Due to similar traits, response to disease may also be similar. Step 3: So a disease can affect the whole crop.

Step 1: Seedless plants cannot be easily multiplied by seeds. Step 2: Vegetative propagation uses parts like stem, root, or leaf. Step 3: Therefore this method is useful for multiplying such plants.

Step 1: In tissue culture, a small plant part is taken and grown. Step 2: It needs materials for growth. Step 3: The nutrient medium provides this support.

Step 1: Self-pollination uses pollen from the same flower or same plant. Step 2: This limits new genetic mixing. Step 3: Therefore variation in offspring may be lower than in cross-pollination.

Step 1: In cross-pollination, pollen goes from one plant to another. Step 2: Traits of two plants can combine. Step 3: More variation can make some offspring better suited to changing environments.

Step 1: After pollination, pollen germinates on the stigma. Step 2: Germination forms a pollen tube. Step 3: Without a pollen tube, the male gamete cannot reach the egg.

Step 1: In pollination, pollen reaches the stigma. Step 2: In fertilization, male and female gametes fuse. Step 3: Pollination may occur first, but fertilization is a separate event.

Step 1: An ovule becomes a seed after fertilization. Step 2: The number of seeds generally depends on the number of fertilized ovules. Step 3: So four fertilized ovules can form four seeds.

Step 1: Wind-pollinated flowers need less insect attraction. Step 2: Wind scatters pollen and many grains may be lost. Step 3: Producing more pollen increases the chance of successful pollination.

Step 1: Insects visit flowers due to nectar or color. Step 2: Sticky pollen grains can attach to their bodies. Step 3: When they visit another flower, pollen can reach the stigma.

Step 1: Sperms are produced in testes. Step 2: Sperm formation needs a temperature slightly below body temperature. Step 3: Therefore testes are located in an external sac.

Step 1: Sperms are produced in testes. Step 2: The vas deferens carries them forward. Step 3: If this tube is blocked, sperms cannot be present on the path to reach the egg.

Step 1: Sperms must move to reach the egg. Step 2: Fluid from accessory glands helps movement and nutrition. Step 3: Without it, sperm function can decrease.

Step 1: Ovulation releases the egg from the ovary. Step 2: Fertilization usually occurs in the fallopian tube. Step 3: If the tube is blocked, gamete fusion becomes difficult.

Step 1: In each cycle the uterus prepares for possible pregnancy. Step 2: Fertilization may form an embryo. Step 3: The thick lining helps implantation and early nourishment.

Step 1: After fertilization, the zygote forms an embryo. Step 2: The embryo must attach to the uterine wall. Step 3: Without attachment, it will not get the support needed for development.

Step 1: The embryo needs nutrients and oxygen from the mother. Step 2: The placenta helps transfer these substances. Step 3: It also helps move wastes from the embryo toward the mother.

Step 1: The uterine lining thickens in preparation for pregnancy. Step 2: If fertilization does not occur, no embryo forms. Step 3: Therefore the lining breaks down and leaves with blood and tissue.