NATS 1572: Class 4 - Nature of Life on Earth

Why is defining life difficult?

Life on Earth is diverse, and characteristics shared by living things can also be found in nonliving things.

Which of the following lists the six characteristics of life discussed in the lecture?

Order, reproduction, growth and development, energy utilization, response to the environment, and evolutionary adaptation

Why is order a necessary but insufficient condition for life?

Living organisms have organized structures, but nonliving things such as crystals can also exhibit order.

Why is reproduction alone insufficient to define life?

Some living organisms cannot reproduce independently, while some nonliving systems can produce copies or patterns.

Why are viruses a challenge when defining life?

Viruses cannot reproduce independently and rely on a host cell’s machinery to replicate.

[Original iClicker] Natural selection is the name given to ________.

The mechanism by which advantageous genetic traits are preferentially passed on from parents to offspring

What are the two key observations that help explain natural selection?

Organisms overproduce offspring and compete for survival, and individuals vary in their traits.

How does natural selection lead to evolutionary change?

Individuals with advantageous heritable traits tend to reproduce more successfully, making those traits more common over generations.

A population contains light-coloured and dark-coloured organisms. They live on a dark background, where predators more easily spot light-coloured individuals. What would natural selection predict over many generations?

Dark-coloured individuals may become more common because they are less visible to predators and may reproduce more successfully.

What is the relationship between mutations and natural selection?

Mutations create genetic variation, and natural selection can favour variants that improve reproductive success in a particular environment.

Why does artificial selection provide evidence relevant to evolution by natural selection?

Selective breeding shows that inherited traits can change in populations over generations.

What is the role of DNA in evolution?

DNA stores hereditary information that can be passed to offspring, and changes in DNA can contribute to evolutionary variation.

[Original iClicker] DNA has four chemical bases, which we call A, T, C, and G. The key reason that DNA strands can replicate when separated is that ________.

A always pairs up with T, and C always pairs up with G.

What is a gene?

A segment of hereditary information associated with a functional product or biological function

What is the relationship between DNA and RNA?

DNA stores hereditary information, while different types of RNA help use and process genetic instructions in cells.

Why are mutations important for evolution?

They introduce genetic changes that can create variation among individuals and be inherited by offspring.

According to the lecture, what is the current working definition of life?

A self-sustained chemical system capable of undergoing Darwinian evolution

What are the three key features of life on Earth that may also be shared by life elsewhere?

Cells, metabolism, and a hereditary molecule

What is metabolism?

The chemical reactions occurring within cells that sustain life, including processes that acquire and use energy and materials

What two basic requirements do cells need for biochemical manufacturing?

A source of raw materials and a source of energy

Why do scientists think that any life beyond Earth would probably require something functionally similar to a cell?

A contained or organized system can coordinate the chemical reactions and material exchanges needed to sustain life.

[Original iClicker] What property of carbon makes it ideal for serving as the basis for life?

Its ability to form strong bonds with itself

Why is carbon particularly suitable for building complex biological molecules?

Carbon can form multiple bonds and bond with itself, creating long chains, branches, and complex molecular structures.

Why is water especially useful as a solvent for life on Earth?

Water’s polarity allows it to interact with and dissolve many substances, making chemical reactions in cells possible.

[Original iClicker] What property of water results in many molecules dissolving in water?

Its polarity

Why might scientists consider liquids other than water when searching for extraterrestrial life?

Alien life may have a different chemistry, potentially allowing it to use another liquid as a solvent.

Why is silicon-based life considered possible but challenging compared with carbon-based life?

Silicon can form four bonds, but its bonding properties and the behaviour of its compounds may make it less suitable for the complex chemistry associated with life as we know it.

What is an extremophile?

An organism that has evolved to thrive in an extreme environment

Why can some microorganisms survive near extremely hot hydrothermal vents?

They have adaptations that allow their cellular structures and proteins to function under high-temperature conditions.

What is an important implication of the diversity of life on Earth for the search for extraterrestrial life?

Scientists should consider microscopic organisms and life adapted to extreme environments, rather than assuming extraterrestrial life must resemble familiar organisms.