Characteristics of life
Name three characteristics that all living organisms share.
What is the smallest level of organization considered alive?
The cell.
What is evolution?
Change in the genetic characteristics of a population over generations.
What are the three domains of life?
What is a hypothesis?
A testable explanation or prediction about an observation.
Why is maintaining homeostasis important for survival?
Homeostasis keeps internal conditions stable (like temperature, pH, and water balance), allowing cells and organisms to function properly.
What is the major difference between prokaryotic and eukaryotic cells?
What does natural selection act on: individuals or populations?
Populations.
Which domain contains organisms with a nucleus?
Eukarya.
Fertilizer experiment:
Independent variable? Dependent variable?
Independent: fertilizer amount/type (what is changed)
A virus has genetic material and can evolve, but scientists debate whether it is alive. Why?
Viruses do not perform all characteristics of life because they cannot reproduce independently or carry out metabolism without a host cell.
An organism has DNA but no nucleus. Is it prokaryotic or eukaryotic?
Prokaryotic, because prokaryotes do not have a nucleus.
Why is this wrong?
"Giraffes evolved long necks because they needed to reach leaves."
Organisms do not develop traits because they need them. Individuals with helpful variations survive and reproduce more, making those traits more common.
Difference between Bacteria and Eukarya?
Bacteria are prokaryotic and lack a nucleus.
Eukarya are eukaryotic and have a nucleus.
Why is a control group important?
It provides a comparison to determine whether the experimental treatment caused the observed results.
Why is fire not considered alive even though it grows and uses energy?
Fire does not have cells, DNA, metabolism, reproduction, or homeostasis. It only appears to show some life-like behaviors.
Put these smallest → largest:
Organism, Molecule, Biosphere, Cell, Tissue, Organ
Molecule → Cell → Tissue → Organ → Organism → Biosphere
How do bacteria become antibiotic resistant?
Some bacteria already have genetic variations that provide resistance. Antibiotics kill susceptible bacteria, while resistant bacteria survive and reproduce.
An organism is single-celled and has no nucleus. What domain(s) could it belong to?
Bacteria or Archaea.
Scientist changes sunlight and measures plant growth:
Independent variable? Dependent variable? Control variables?
Why is it difficult to create one perfect definition of life?
Some biological entities, like viruses, show some characteristics of life but not all, making the boundary between living and nonliving difficult to define.
Why are cells considered the basic unit of life?
Cells are the smallest structures capable of performing all processes necessary for life.
Explain variation → environment → survival/reproduction → evolution.
Why are viruses difficult to classify as living?
They have genetic material and evolve but cannot reproduce or metabolize independently.
Why is a wrong hypothesis not a failed experiment?
Experiments test ideas. A result that does not support a hypothesis still provides scientific information.