Origins of Life, Cell Theory & Key Contributors

30 Question-and-Answer flashcards covering spontaneous generation experiments, theories of life’s origin, extremophile evidence, biological definitions, and cell theory with its major contributors.

What idea did Francesco Redi’s 1668 meat-jar experiment refute?

Spontaneous generation (abiogenesis) of maggots from rotting meat.

In Redi’s experiment, where did maggots appear and why?

Only on the uncovered meat because flies laid eggs there.

Which English priest boiled mutton broth in 1745, observed cloudiness, and mistakenly supported spontaneous generation?

John Needham.

Why was Needham’s conclusion flawed?

He did not boil the broth long enough to kill all microorganisms.

How did Lazzaro Spallanzani’s 1767 broth experiment challenge Needham?

Only his open flask became cloudy; the sealed flask stayed sterile, showing microbes came from the air.

What objection did abiogenesis supporters raise against Spallanzani’s sealed flask?

They claimed removing air prevented spontaneous generation.

Which device did Louis Pasteur use in 1861 to finally disprove spontaneous generation?

A swan-neck (gooseneck) flask.

What key observation came from Pasteur’s swan-neck flask when the neck remained intact?

No microbial growth occurred because airborne microbes were trapped in the curved neck.

What happened when Pasteur broke the swan-neck?

Microorganisms quickly grew in the broth, proving they entered from the air.

State the modern principle supported by Redi, Spallanzani, and Pasteur.

Biogenesis – life arises from pre-existing life.

Define ‘panspermia.’

The hypothesis that life, or its building blocks, arrived on Earth from space via meteors or cosmic dust.

Which scientist popularized panspermia?

Svante Arrhenius.

What 1953 experiment simulated early-Earth conditions and produced amino acids?

The Miller-Urey experiment.

Summarize the ‘primordial soup’ hypothesis.

Organic molecules accumulated in Earth’s early oceans, randomly assembling into increasingly complex compounds that led to the first cells.

What does divine creation (creationism) propose about life’s origin?

Life and the universe were created by a supernatural being, traditionally in six days.

Give two modern lines of evidence that broaden our concept of where life can exist.

Discovery of extremophiles in deep-sea vents and beneath ice; analysis of ancient DNA showing adaptation over time.

Define biology in one sentence.

Biology is the scientific study of life and living processes, from microbes to whales.

Which two approaches make biology both discovery- and hypothesis-based?

The use of the scientific method and technology/tools for investigation.

Who coined the term “cell,” and in what year did he publish Micrographia?

Robert Hooke; 1665.

What structure did Hooke observe in cork that led to the term ‘cell’?

Cell walls forming tiny compartments like small rooms.

Name the Dutch microscopist who first observed living cells (‘animalcules’).

Antoine van Leeuwenhoek.

How powerful was Leeuwenhoek’s best single-lens microscope?

About 270× magnification.

List the three tenets of the classical Cell Theory.

1) All organisms are composed of one or more cells. 2) The cell is the basic unit of structure and function. 3) Cells arise only from pre-existing cells.

Which botanist concluded that all plants are made of cells?

Matthias Schleiden.

Which zoologist/physiologist stated that all animals are made of cells and helped found histology?

Theodor Schwann.

Who added the third tenet to cell theory, emphasizing that cells come from existing cells?

Rudolf Virchow.

What medical insight did Virchow contribute regarding disease?

Diseases originate in individual cells (cellular pathology).

What are Schwann cells and why are they important?

Cells that form the myelin sheath insulating peripheral nerve fibers.

Which discovery shows life’s resilience in ‘harsh, unexpected environments’?

Microbes thriving in deep-ocean vents, under polar ice, and other extreme habitats.

What key astrobiological question arises from modern discoveries about extremophiles?

Can life exist elsewhere in the universe beyond Earth?