Railway Science (Biology-Reproduction in Animals)

Female sex hormones secreted by the ovaries - Oestrogen (Estrogen) and Progesterone. Male sex hormone - Testosterone (bone mass, fat distribution, muscle mass and strength, and the production of red blood cells and sperm).

There are several factors for determining the sex of individuals which are genetic factors and environmental factors. The phenomena of changing sex at some point during their lives are called sequential hermaphroditism.
It is also called dichogamy. The snail is born as a male but eventually changes into a female.

Menstruation is normal vaginal bleeding that occurs as part of a woman's monthly cycle. Every month, the body prepares for pregnancy. If no pregnancy occurs, the uterus, or womb, sheds its lining.
The menstrual blood is partly blood and partly tissue from inside the uterus. The menstrual cycle is controlled by hormones - luteinizing hormone, follicle-stimulating hormone and the female sex hormones, estrogen and progesterone.

It is a unique stage of human development and an important time for laying the foundations of good health. Adolescents experience rapid physical, cognitive and psychosocial growth. It is a time for growth spurts and puberty changes.

The sex chromosomes (X and Y chromosomes) determine the biological sex of an individual. Mothers only pass on X chromosomes to the child. Females inherit an X chromosome from the father for a XX genotype, while males inherit a Y chromosome from the father for a XY genotype.

It is part of a seed or bud that contains the earliest forms of a plant's roots, stem and leaves. The embryo develops after a fertilized adult plant flowers and is generally contained within a seed or bud.
Endosperm - Surrounds and nourishes the embryo in the seeds of angiosperms (flowering plants).
Cotyledons - A leaf of the embryo of a seeding plant. Seed coat - It protects the embryo and transmits information regarding the external environment.

Temperatures above 30°C produce all females, while temperatures below 25°C produce all male broods. Reptiles are a class of vertebrates made up mostly of snakes, turtles, lizards and crocodilians. These animals are most easily recognized by their dry, scaly skin. They are cold blooded animals.

Chromosomes - A chromosome is a long DNA molecule with part or all of the genetic material of an organism. First discovered by - Walther Flemming (1882). Chromosomes in various organisms : Cat - 38, Dog - 78, Rice - 24, Pea - 14, Housefly -12, Apple - 34, Maize - 20, Potato - 48, Butterfly - 360, Onion - 16, Elephant - 56, Cow - 60, Chimpanzee - 48.

Embryo is the early developmental stage of an animal while it is in the egg or within the uterus of the mother. Eggs are produced in the ovaries, which are normally situated towards a woman's abdomen below the kidneys. After ovulation, the egg lives for 12 to 24 hours.
Placenta is an organ that develops in the uterus during pregnancy. It provides oxygen and nutrients to a growing baby. Zygote fertilized egg cell that results from the union of a female gamete (egg, or ovum) with a male gamete (sperm).

Menstruation - When an ovum is unfertilized, the uterus lining sheds and leads to a hemorrhage. Menarche - In a girl, menstruation starts from the age of 10 to 15 when she attains puberty. The ending of menstruation is known as menopause which takes place at the age range of 50.