Biology

• The full form of DNA is deoxyribonucleic acid.
• Most cells in a human body contain 46 chromosomes
• Sperm cells and egg cells are specialized cells known as gamete.
• Sperm cell and egg cell have 23 chromosomes
• The joining of a sperm cell with an egg cell is called fertilisation
• The new cell that is formed when the nucleus of the sperm cell and the egg cell is called a zygote.
• A person with XX chromosomes is a female
• A person with XY chromosome is a male.
• All eggs contain an X chromosome, while half of all sperm cells contain an X chromosome and other half contain Y chromosome.
• The difference between individuals belonging to the same species are called variation
• Differences in the DNA of organisms within species are called genetic differences.
• Special cells called root hairs grow out of the surface of roots
• Each root hair is part of a single cell
• Water moves into the root hair from the soil. It passes through the cell wall and cell membrane of the cell, and into the cytoplasm.
• Root hairs increase the total area available for water absorption by plants
• Minerals, including magnesium and nitrate move into the root hair cell along with water
• In the center of root hairs are very special cells called xylem vessels
• Xylem vessels are long, tube-like cells and are dead. All of their contents are gone.
• Plants need water because it helps them stay upright
• As water moves along the xylem vessels, it carries dissolved mineral salts
• When water evaporates, it takes heat with it So when water evaporates from the cell, it cools it.
• In photosynthesis, plants change water and carbon dioxide into glucose and oxygen.
• If we have more protein than we need, the liver changes the molecules into Urea
• Urea is a poisonous substance
• Renal means "to do with kidneys"
• Kidneys remove excess water from the blood and the urea dissolves in the water called urine
• The urine made in each kidney flows down a tube called ureter
• For the first nine months of its life, a new human being grows inside its mother called a fetus
• Protein is needed for fetus to produce new cells and grow and hemoglobin for the mother and the fetus.