A2.2. HL Origin and Evolution of cells (4/4)

What do we believe was the order of cells evolving?

Prokaryotes evolved first, and eukaryotes appeared much later.

What does endo- mean?

Inside.

What does -symbiosis mean?

Together.

What does heterotrophic mean?

Consumes other organisms for nutrients.

What does autotrophic mean?

Produces its own carbon compounds.

What does the endosymbiotic theory state?

Early eukaryotes engulfed prokaryotes that evolved endosymbiotically to become organelles of later eukaryotes.

Which organelles does IB focus on as having once been independent prokaryotes?

Mitochondria and chloroplasts.

What is the evidence that mitochondria and chloroplasts are similar to prokaryotes?

They have their own circular DNA and 70S ribosomes, synthesize their own proteins, and reproduce independently by binary fission.

What element of chloroplast and mitochondrial structure indicates they used to be prokaryotes?

They are double membraned.

Where would mitochondria and chloroplasts have gotten a double membrane?

From their original membrane and the one gained during the engulfing process.

What is cell differentiation?

The process by which cells in multicellular organisms develop specific functions.

What is cell specialization?

The development of cells with different structures and functions.

When does cell specialization occur?

During embryonic development, when certain genes are expressed while others are not.

What are stem cells?

Undifferentiated cells that can differentiate and specialize into various cell types.

What genes are “on” in a neuron?

Genes specific to neuron function.

What kinds of genes are “on” in all cells?

Housekeeping genes (e.g., those for ribosome production).

What’s a downside of having specialized cells?

Specialized cells cannot survive independently outside the body.

What are some advantages of being multicellular?

Longer lifespans, larger sizes for ecosystem roles, and the ability to differentiate for efficiency and complexity.

What organisms are multicellular?

All plants, animals, certain fungi, and eukaryotic algae.