Science Lecture Notes: Living World and Physical World

A comprehensive set of flashcards covering male and female reproductive systems, genetics, DNA replication, mitosis versus meiosis, evolutionary theories by Darwin and Lamarck, and basic physics concepts of motion.

What are the functions of the testes?

Two egg-shaped reproductive glands (gonads) that produce sperm for reproduction and secrete testosterone for development and maturation.

Describe the purpose of the scrotum.

An external pouch and muscular tissue behind the penis that acts as a protective container for the testes and regulates body temperature to keep testes cool for sperm production.

What is the function of the epididymis?

A narrow, tightly coiled tube on top of the testes where sperm cells are stored, matured, and gain the ability to swim before ejaculation.

What is the role of the vas deferens?

A direct pathway for sperm from the epididymis to the urethra that contracts to move sperm, facilitating its transport out of the body.

Describe the functions of the ovaries.

Small, oval-shaped organs in the female reproductive system that store and release eggs and produce vital hormones.

What happens in the Fallopian Tube?

These two thin, muscular tubes connect the ovaries to the uterus, serve as a pathway for eggs, and are the primary site of fertilisation.

What are the functions of the uterus?

A body inside the female reproductive system where menstruation occurs (shedding the inner layer), the lining grows monthly for a potential baby, and it houses the growing fetus while providing nutrients.

Identify the male and female gametes and their chromosome count.

The male gamete is sperm and the female gamete is the egg. Each contains $23$ chromosomes, and they fuse during fertilisation to create a baby with $46$ chromosomes.

Define a gene.

A unit of heredity that carries physical and biological features from parents to children; chemically, it is a segment within a strand of DNA located on a chromosome.

Explain the role of gametes in the transmission of heritable characteristics.

Gametes are the only cells that physically carry genetic information; fertilisation fuses them to restore the full chromosome number ($46$) while combining maternal and paternal alleles.

Describe the structure of DNA and how it is packed.

DNA has a double helix structure with complementary pairs ($AT$ and $GC$). It is packed into chromosomes by histone proteins.

What is Watson-Crick’s model of DNA replication?

The double helix unwinds and two strands separate, each acting as a base for a new complementary strand, resulting in two identical DNA molecules.

Why is it important for DNA replication to be exact?

It ensures each new cell receives correct genetic information and prevents mutations that could create faulty proteins, disease, or cell malfunction.

Compare the results and purposes of Mitosis and Meiosis.

Mitosis results in two identical daughter cells for growth and tissue repair. Meiosis results in four unique haploid daughter cells to produce gametes for sexual reproduction.

What is the difference between a dominant and a recessive allele?

A dominant allele shows its trait if one copy is present (e.g., $Bb$), while a recessive allele only shows its trait if both copies are present (e.g., $bb$).

What were the results of Mendel’s experiment crossing tall and short pure-breeding pea plants?

The dominant trait always appeared in the first generation, and when those offspring were crossed, the traits appeared in a $3:1$ ratio (dominant:recessive).

Define mutation and name three types related to DNA base units.

A mutation is a change in the structure of a gene. Types include alteration of single base units (substitution), deletion, and insertion.

What is a frameshift mutation?

A mutation caused by insertion or deletion that scrambles the codon instructions, producing a completely different amino acid sequence.

List three advantages of GM foods biotechnology.

Higher crop yields (pest and drought resistance), reduced pesticide use (e.g., $Bt$ corn), and increased nutritional value (e.g., golden rice with Vitamin A).

Explain the relationship between natural selection and evolution.

Organisms better suited to their environment survive and reproduce more successfully. Over many generations, passing these advantageous alleles makes the trait common, leading to the evolution of the species.

What was Jean Baptiste Lamarck’s contribution to evolution theory?

One of the first to propose species change over time, suggesting organisms change because they need to adapt and that acquired traits through use or disuse are passed to offspring.

How did Alfred Russel Wallace and Charles Darwin contribute to the theory of evolution?

They co-presented the idea in $1858$ that individuals with advantageous variations survive and reproduce more, passing traits down until the species changes over generations.

How does the development of antibiotic resistance in bacteria demonstrate natural selection?

Some bacteria have a mutation making them resistant; when antibiotics are used, the resistant ones survive and reproduce until the whole population becomes resistant.

What are the three main types of evidence for evolution?

Fossil evidence (transitional forms), similar anatomy (homologous structures like human arms and whale flippers), and DNA evidence (e.g., humans and chimpanzees share $98-99$% of DNA).

What is Tiktaalik and why is it significant?

It is a fossil that has traits between fish and amphibians, showcasing how one group evolved into another.

Differentiate between scalars and vectors and give examples of each.

Scalars have only magnitude (speed, distance, time, mass). Vectors have both magnitude and direction (velocity, displacement, force, acceleration).

Define distance versus displacement.

Distance is the total length of the path travelled (scalar), while displacement is the change of position measured in a straight line from start to finish (vector).

What is the formula for average velocity?

$$\text{Average velocity} = \frac{\text{total displacement}}{\text{total time}}$$