Rock Layers Right at the K-Pg Boundary Have Enriched Concentrations

question 13

Multiple Choice

Rock layers right at the K-Pg boundary have enriched concentrations of the element iridium.This is significant for understanding the mass extinction that happened at the time,because ________.

• A) iridium is toxic to life and could have killed off many species
• B) iridium is very rare in the Earth's crust but relatively common in meteorites
• C) iridium forms under conditions of extreme shock and heat
• D) iridium would have caused an episode of severe acid rain
• E) iridium-rich dust is particularly effective at blocking incoming solar radiation

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Definitions:

Hypothalamus

A brain structure, located just above the brain stem, that performs a number of important tasks, including the regulation of hunger, thirst, and sexual desire, and connects the nervous system to the endocrine system.

Gonads

The primary reproductive organs that produce gametes (sperm in males, ova in females) and sex hormones, including testes in males and ovaries in females.

Secondary Sex Characteristics

The anatomical and physiological signs that outwardly distinguish males from females.

Menarche

The first occurrence of menstruation in girls, marking a significant milestone in female puberty and reproductive maturity.