General Science Term 3

What is the Big Bang Theory?

A theory that 13.8 billion years ago, the universe began as an infinitely hot and dense point (singularity) that rapidly expanded, forming all matter and radiation.

What occurred immediately after the Big Bang?

The rapid expansion slowed, allowing the formation of matter, radiation, and fundamental particles.

What does current evidence suggest about the universe's expansion?

The universe has been expanding since the Big Bang and continues to expand today.

What are the main types of evidence supporting the Big Bang?

1. Abundance of light elements 2. Cosmic Microwave Background (CMB) Radiation 3. Redshift of galaxies

How does the abundance of light elements support the Big Bang?

Hydrogen, helium, and lithium formed in the early universe. Their predicted ratios match what is observed in ancient stars.

What is the CMB radiation and why is it important?

It’s leftover radiation from about 380,000 years after the Big Bang, when the universe cooled enough for protons and electrons to combine.

What does redshift tell us about the universe?

It shows that distant galaxies are moving away from us, meaning the universe is expanding.

What is Hubble’s Law?

The farther away a galaxy is, the faster it is moving away from us.

What happens during nuclear fusion?

Light atomic nuclei combine to form heavier nuclei, releasing energy due to a loss in mass.

What is spectral analysis in astronomy?

A technique to identify a star’s composition, temperature, motion, and life stage using the light it emits and absorbs.

Why is spectral analysis sometimes called a star’s fingerprint?

Because each element absorbs/emits light at specific wavelengths, giving each star a unique spectral pattern.

How does a star form?

In molecular clouds, gas clumps together and heats up. When hot enough, it glows as a protostar and begins nuclear fusion.

What is a Main Sequence star?

A star in the stable phase where hydrogen fuses into helium, releasing energy. Larger stars spend less time in this phase.

What happens after a star runs out of hydrogen?

Helium begins to fuse into carbon and the star expands into a Red Giant (or Red Supergiant if it's large).

What happens when helium in a star runs out?

The outer layers drift away as a planetary nebula or the star explodes in a supernova, depending on its mass.

What is a white dwarf and what happens to it over time?

A white dwarf is a dense, cooling stellar remnant. Over time, it fades into a black dwarf when all light is gone.

What happens to very massive stars after a supernova?

They become either neutron stars or black holes.

What is an Astronomical Unit?

A standard measure for space distances, approximately the average distance between Earth and the Sun.

What is a Black Hole?

An area with extremely high gravitational pull from which no light, radiation, or matter can escape.

What is a Celestial Body?

Natural objects located outside of Earth's atmosphere.

What is a Constellation?

A group of stars that form a recognizable pattern.

What is a Galaxy?

A massive system containing stars, stellar remnants, interstellar gas, dust, and dark matter, all bound together by gravity.

What is a Light Year?

The distance light travels in one year, used to measure cosmic distances.

What is a Nebula?

A giant cloud of dust and gas occupying space between stars.

What is a Planet?

A celestial body that orbits a star, is massive enough to be rounded by its own gravity, but not massive enough to start nuclear fusion.

What is a Star?

A luminous sphere of plasma held together by its own gravity.

What is the Universe?

The totality of everything that exists.

What does DNA stand for?

Deoxyribonucleic Acid.

What is DNA’s function?

Carries hereditary information and controls cell activities.

Where is DNA located?

Inside the cell nucleus, within chromosomes.

What is the shape of DNA?

A double helix.

What is the DNA backbone made of?

Deoxyribose and phosphates connected to nitrogenous bases.

What is a Gene?

A DNA segment with instructions for building proteins.

What is Genetics?

The study of how traits are inherited.

What is a Genome?

The complete genetic material of an organism.

What is Helicase?

An enzyme that unwinds DNA for replication.

What is Mitosis?

Cell division creating two identical daughter cells.

Why does Mitosis occur?

For growth, repair, and asexual reproduction.

Where does Mitosis occur?

In somatic (non-reproductive) cells.

What happens during Interphase (Mitosis)?

Cell grows and duplicates chromosomes.

What happens during Prophase?

Chromosomes condense, spindles form, and nuclear envelope breaks.

What happens during Metaphase?

Chromosomes align in the middle; spindle fibers attach.

What happens during Anaphase?

Chromatids are pulled apart.

What happens during Telophase?

Nuclear envelope reforms and spindle fibers detach.

What is Cytokinesis?

Cytoplasm divides, forming two cells.

What is Meiosis?

Cell division creating four genetically unique daughter cells.

How many chromosomes do meiosis products have?

Half the original cell’s number.

What does Meiosis produce?

Gametes for sexual reproduction.

Where does Meiosis occur?

In germ cells of eukaryotes.

Why is Meiosis important?

It introduces genetic variation.

What are Alleles?

Alternate forms of the same gene.

What is a Dominant gene?

A gene that masks the effect of a recessive one.

What letter represents a dominant allele?

An uppercase letter (e.g., F).

What letter represents a recessive allele?

A lowercase letter (e.g., f).

What is Homozygous Dominant?

FF.

What is Homozygous Recessive?

ff.

What is Heterozygous?

Ff.

What is Genotype?

The gene combination (e.g., Ff).

What is Phenotype?

The physical trait expressed.

What is a Pedigree chart?

A diagram tracking trait inheritance through generations.

What determines traits?

Genes.

What else influences gene expression?

Environmental factors.

What are inherited traits?

Traits passed via DNA from parents.

What are acquired traits?

Traits learned or developed through life.

What are the two types of adaptations?

Structural and Behavioural.

What is a structural adaptation?

A physical trait that aids survival.

What is a behavioural adaptation?

A change in behaviour that aids survival.

How do adaptations arise?

Through natural variations.

What is evolution?

Genetic change in a population over generations.

What does evolution explain?

The diversity, complexity, and adaptability of life.

Who proposed evolution before Darwin?

Jean-Baptiste Lamarck.

What were Lamarck’s two hypotheses?

Use/disuse of traits and inheritance of acquired traits.

What did Darwin notice about species?

They have variations in traits.

What did Darwin propose?

Favorable traits improve survival and are passed on.

What do fossil records show?

Organisms have changed over long periods.

What is chemical evidence of evolution?

DNA comparisons between ancient and modern organisms.

What do similar DNA sequences suggest?

A common evolutionary ancestor.

What are homologous structures?

Similar anatomical features from a shared ancestor.

What does biogeography study?

Species distribution showing evolutionary links.

What does comparative embryology show?

Similar embryo development across species suggests shared ancestry.

What is natural selection?

Organisms with better traits survive and reproduce more.

What role does evolution play in natural selection?

It introduces variation for natural selection to act on.

What are the four principles of natural selection?

Adaptation, Variation, Isolation, Selection.

What is the principle of Adaptation?

Traits that help survival and reproduction become more common.

What is the principle of Variation?

Differences in traits among individuals in a population.

What is the principle of Isolation?

Separated populations evolve independently.

What is the principle of Selection?

Environmental pressures favor some traits.

How does natural selection affect populations?

Advantageous traits become more common over time.

Can natural selection lead to new species?

Yes, especially with isolation.

Why is genetic variation important?

It’s the raw material for evolution via natural selection.