Biology Notes (Semester 1)

This covers REPRODUCTION, DNA, GENETICS, MITOSIS and MEIOSIS. (This is for Semester 1, Year 10 at BGGS)

What is sexual reproduction?

A process involving the fusion of sex cells (gametes) to form a fertilized zygote.

What are the male and female gametes in animals?

Male gametes are sperm; female gametes are ova.

What is the main advantage of sexual reproduction?

It leads to genetic diversity in offspring, enhancing survival in changing environments.

What is a disadvantage of sexual reproduction?

It is energetically expensive and requires finding and attracting mates.

What is asexual reproduction?

A process where offspring are produced without gametes, resulting in genetically identical clones of the parent.

What is binary fission?

A form of asexual reproduction in single-celled organisms like bacteria, where a parent splits into two.

What is the menstrual cycle?

A regulated cycle averaging 28 days in females involving menstruation and ovulation.

What is ovulation?

The release of an ovum from the ovary during the menstrual cycle.

What hormone triggers ovulation?

Luteinising Hormone (LH) peaks mid-cycle to induce ovulation.

What is the role of the placenta during pregnancy?

It allows the exchange of oxygen, nutrients, and waste between mother and embryo.

What is DNA?

Deoxyribonucleic acid, a complex molecule storing the genetic blueprint of organisms.

What are the four nitrogenous bases of DNA?

Adenine (A), Thymine (T), Guanine (G), and Cytosine (C).

What does base pairing in DNA entail?

A pairs with T, and G pairs with C, held together by hydrogen bonds.

What is a karyotype?

An arrangement of chromosomes that can be used to detect mutations or abnormalities.

How many chromosomes do humans have?

Humans have 46 chromosomes, organized into 23 pairs.

What is the difference between somatic cells and gametes?

Somatic cells are diploid (2n) with pairs of chromosomes, while gametes are haploid (n) with one set of chromosomes.

What is mitosis?

A process of nuclear division producing two genetically identical diploid daughter cells.

What is meiosis?

A type of nuclear division that produces four haploid daughter cells, each genetically unique.

What is incomplete dominance?

A form of inheritance where a heterozygous individual shows a blended phenotype.

What is a Punnett square?

A grid used to predict genotypes and phenotypes in genetic crosses.

What is X-linked inheritance?

Inheritance of traits located on the X chromosome, often affecting males more frequently.