Explanation

• The lungs exchange gases — they absorb oxygen (O₂) and release carbon dioxide (CO₂).
• This process is essential for respiration and energy production in the body.

Last verified on 05-09-2026

Explanation

• Paleolithic = Old Stone Age; people hunted animals and gathered wild plants.
• "Old Stone Age," the earliest and longest human era (roughly 2.6 million years ago to about 10,000 BCE).

Explanation

Sandra Harding

• Developed feminist epistemology; identified three approaches:
• Feminist empiricism (1986, The Science Question in Feminism)
• Standpoint theory (1991, Whose Science? Whose Knowledge?)
• Postmodern feminism (1986, later works)

Additional information

• Simone de Beauvoir — The Second Sex (1949)
• Judith Butler — Gender Trouble (1990)
• Betty Friedan — The Feminine Mystique (1963)

Explanation

• The Chalcolithic Period (also called the Copper Age):
• Marks the transition between the Stone Age and the Bronze Age
• Defined by the simultaneous use of stone and copper tools
• Name comes from the Greek chalcos (copper) and lithos (stone)
• It's the period when humans first began working with metal

Explanation

• The Earth's outermost layer is called the Crust.
• The crust is the thin, solid outer layer where humans, animals, and plants live.
• It is located above the mantle, outer core, and inner core.
• It is made mainly of rocks and minerals.

Additional information:

• Earth's Layers (Outer to Inner): Crust → Mantle → Outer Core → Inner Core
• Crust Thickness: About 5–70 km
• Mantle Thickness: About 2,900 km
• Outer Core Thickness: About 2,260 km
• Inner Core Radius: About 1,220 km

Last verified on 04-08-2026