Lecture 5: Organized Movement in Single-Celled Organisms

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What is chemotaxis?

The movement of cells in response to mechanical vibration
The random migration of cells in response to light signals
The directed migration of cells in response to concentration gradients of extracellular signals (correct)
The movement of cells towards areas with high pressure

How do rattlesnakes use chemical cues to track down prey?

By comparing the concentration of chemicals on their left and right sides (correct)
By moving towards areas with high atmospheric pressure
By detecting vibrations in the ground caused by their prey
By using their sense of taste to follow the scent left by their prey

What is the purpose of the forked tongue in rattlesnakes when hunting?

To pick up large non-volatile chemicals exuded by the prey (correct)
To help the snake camouflage itself in its environment
To sense vibrations in the air caused by movement
To sting and inject venom into the prey

What happens if the concentration of a chemical cue is greater on the right for a rattlesnake?

The snake moves towards the right (A) Signup and view all the answers

Why is comparing concentration on the two sides impossible for bacteria detecting chemical signals?

Bacteria cannot steer their movement based on comparing signals between their sensory organs (A) Signup and view all the answers

What is one problem faced by bacteria during chemotaxis due to the density of the subject?

Bacteria experience inertia which affects their movement (C) Signup and view all the answers

What does the Dead Sea Reynolds Number (Re) represent?

Efficiency of organism swimming (A) Signup and view all the answers

Why is viscosity negligible for large animals according to the text?

All the above (D) Signup and view all the answers

What characterizes laminar flow in fluids?

Smooth and regular flow paths (C) Signup and view all the answers

Why is viscosity all-important for small organisms like bacteria?

Small organisms have lower Reynolds Numbers (Re) (B) Signup and view all the answers

What is a possible solution to the 'swimming in syrup' problem mentioned in the text?

Utilize behavior like run/tumble to navigate (A) Signup and view all the answers

Why do fish have shapes that maximize laminar flow and minimize turbulent flow?

To reduce friction in water (D) Signup and view all the answers

What is the main mechanism bacteria use to navigate in response to chemical cues?

Growth of pseudopods in a biased manner (B) Signup and view all the answers

Why is direct use of sensory input for course correction not possible for bacteria?

They rely on behavior patterns that are internally regulated (C) Signup and view all the answers

What type of locomotory memory works for tracking chemical traces in bacteria?

Growth of pseudopods in a biased manner (C) Signup and view all the answers

What does increasing size help with in bacteria's navigation?

Better targeting through sampling changes over time (A) Signup and view all the answers

What is the main limitation regarding built-in behavior patterns in bacteria?

Limited modulation by temporal cues (B) Signup and view all the answers

What plays a key role in steering amoeboid movement towards the right direction in response to a chemical gradient?

Continuous projection of pseudopods (C) Signup and view all the answers