Life Science and Astronomy Lecture Notes

Comprehensive practice flashcards covering cellular respiration, photosynthesis, optical and radio telescopes, galaxies, constellations, celestial bodies (meteors, comets, asteroids, dwarf planets), planetary data, and the structure and fusion processes of the Sun.

What is the biological definition of respiration?

The process of releasing energy from food.

What is the chemical equation for cellular respiration?

$$O_2 + C_6H_{12}O_6 \rightarrow H_2O + CO_2 + \text{ATP (energy)}$$

In what units is food energy measured, and how is it determined?

Food energy is measured in kilojoules ($kJ$) or kilocalories ($kcal$) using calorimetry, which measures the amount of heat released that raises the temperature of water.

What is the chemical equation for photosynthesis?

$$CO_2 + H_2O \rightarrow C_6H_{12}O_6 + O_2$$

How do the stomata of xerophytes and hydrophytes differ in adaptation?

Xerophytes have fewer stomata, primarily at the bottom of their leaves, to reduce water loss; hydrophytes have stomata at the top of their leaves.

What green pigment is responsible for photosynthesis, and what are the structural components of a chloroplast?

Chlorophyll; the chloroplast consists of an outer membrane, inner membrane, stroma, granum, and thylakoid.

Who was the first person to observe the Milky Way through a telescope and in what year?

Galileo Galilei in 1610.

What are the structural features and location of the Southern African Large Telescope (SALT)?

An optical telescope located in Sutherland, Northern Cape, composed of 91 hexagonal (six-sided) mirrors controlled by computers to work as one large mirror, capable of rotating almost $360^{\circ}$ in about 3 minutes.

What is the Square Kilometre Array (SKA), and what telescope served as its precursor?

A composite radio telescope consisting of thousands of individual radio telescopes working together as one; its precursor is the South African MeerKAT telescope, launched in January 2018.

What is a galaxy, and what are the three major types of galaxies?

A huge group of stars, gas, and dust orbiting a common centre held together by gravity; the three major types are spiral, elliptical, and irregular.

What was the Greek origin of the name 'Milky Way,' and where is the Sun located within it?

The Greeks called it "galaxies kuklos" (or "galaxies kaklos"), meaning "milk circle"; the Sun is at the centre of the solar system, but not at the centre of the Milky Way.

What is the second closest star to Earth, and how far away is it?

Alpha Centauri, which is $4.2\text{ light years}$ away (the closest star is the Sun).

What is a constellation, and what was the earliest star map?

A constellation is a star pattern; the zodiac is the earliest star map, consisting of a map of 12 constellations.

What is the distinction between a meteor, a meteorite, and a meteoroid?

A meteoroid is a small piece of rock broken off an asteroid or comet; a meteor is a bright streak of light ("shooting star") created when a meteoroid burns up in the atmosphere; a meteorite is a meteoroid that enters Earth's atmosphere and strikes the ground.

What is a comet, where are around 70,000 comets located, and when do they become visible?

Comets are masses of ice, rock, dust, and frozen gases located in the Kuiper belt; they are only visible when they approach the Sun, where the ice melts and releases gas and dust clouds.

What is a dwarf planet, and what are five examples?

A small celestial body that orbits a star and has not cleared all debris from its orbit; examples include Pluto, Eris, Haumea, Makemake, and Ceres.

Where is the Asteroid belt located, and what happens when a car-sized asteroid enters Earth's atmosphere?

Between Mars and Jupiter (containing about 300,000 asteroids); once a year, a car-sized asteroid falls into Earth's atmosphere, producing a fireball that usually burns up before reaching the ground.

What are the values of a light minute, light hour, and light year in kilometres?

A light minute is $18\,000\,000\text{ km}$ ($18\text{ million km}$), a light hour is $1\,000\,000\,000\text{ km}$ ($1\text{ billion km}$), and a light year is $10\,000\,000\,000\,000\text{ km}$ ($10\text{ trillion km}$).

What is the definition of a moon?

A natural satellite that orbits a planet or dwarf planet.

What three criteria must a celestial body meet to be classified as a planet?

It must be in orbit around a Sun, its gravity must pull it into a round shape, and it must have cleared the neighbourhood around its orbit of objects.

What is the difference between planetary rotation and revolution?

Rotation is the planet spinning on its own axis, whereas revolution is the planet orbiting around the Sun.

What are the key physical and orbital characteristics of Mercury?

Closest terrestrial planet to the Sun; diameter of $4\,880\text{ km}$; distance of $57.4\text{ million km}$; rotation of about $59\text{ Earth days}$; revolution of about $88\text{ Earth days}$; surface temperature of $-180\,^{\circ}\text{C}\text{ to }430\,^{\circ}\text{C}$; no moons; heavy composition consisting mainly of iron, very thin atmosphere, and large surface craters.

What are the key characteristics of Venus?

Second terrestrial planet from the Sun; diameter of $12\,104\text{ km}$; distance of $108.2\text{ million km}$; rotation of about $243\text{ Earth days}$; revolution of about $225\text{ Earth days}$; surface temperature of about $464\,^{\circ}\text{C}$; no moons.

Why is Mars called the 'red planet,' and what are its orbital and physical metrics?

Iron materials in the soil oxidize (rust), turning the surface red; it is the fourth terrestrial planet; diameter of $6\,774\text{ km}$; distance of $225\text{ million km}$; rotation of $24\text{ hours and }39\text{ minutes}$; revolution of about $687\text{ Earth days}$; surface temperature of $-153\,^{\circ}\text{C}\text{ to }20\,^{\circ}\text{C}$; has 2 moons.

What are the orbital and physical characteristics of Jupiter?

Fifth planet from the Sun; gas planet; diameter of $139\,822\text{ km}$; distance of $778\text{ million km}$; rotation of about $10\text{ Earth hours}$; revolution of about $11.86\text{ Earth years}$; surface temperature of $-183\,^{\circ}\text{C}\text{ to }-108\,^{\circ}\text{C}$.

What are the key characteristics of Saturn?

Sixth planet from the Sun; gas planet; diameter of $120\,000\text{ km}$; distance of $1.42\text{ billion km}$; rotation of about $10\text{ hours}$; surface temperature of $-140\,^{\circ}\text{C}$.

What are the key characteristics of Uranus?

Seventh planet from the Sun; ice planet; diameter of $51\,118\text{ km}$; distance of $2.87\text{ billion km}$; rotation of $17\text{ hours}$; revolution of about $84\text{ Earth years}$; surface temperature of $-224\,^{\circ}\text{C}$; has 27 moons.

What are the key characteristics of Neptune?

Eighth planet from the Sun; ice planet; diameter of $49\,244\text{ km}$; distance of $4.5\text{ billion km}$; rotation of $16\text{ hours}$; revolution of $165\text{ Earth years}$; surface temperature of $-224\,^{\circ}\text{C}$; has 14 moons (labeled 16 in raw notes).

How does the Sun generate energy, and what reaction occurs every second?

Through nuclear fusion ($H + H \rightarrow He + \text{energy}$), converting $700\text{ million tons}$ of hydrogen into $695\text{ million tons}$ of helium every second, releasing $386\text{ quintillion megawatts}$ of energy (equivalent to $100\text{ billion tons}$ of dynamite exploding per second).

What are the age, size, distance, and chemical composition of the Sun?

A medium-sized star, $4.6\text{ billion years}$ old, located $150\text{ million km}$ from Earth, composed of about $71\%$ hydrogen, about $27\%$ helium, and $2\%$ trace elements (carbon, oxygen, nitrogen).

What is the temperature of the Sun's core versus its surface, and how long does energy take to travel from the core to the surface?

The core is approximately $\pm 15\text{ million}\,^{\circ}\text{C}$ and the surface is about $5\,500\,^{\circ}\text{C}$; energy produced in the core takes approximately $\pm 17\,000\text{ to }100\,000\text{ years}$ to reach the surface.