A2.2.7 Processes of life in unicellular organisms

List the key functions of life in unicellular organisms.

Homeostasis, Metabolism, Nutrition, Movement, Excretion, Growth, Response to stimuli, Reproduction.

What is the mnemonic to remember the key functions of life?

"Hot Moms Need Many Exciting Games, Really Relaxing."

Define homeostasis.

Homeostasis is the process of maintaining a stable internal environment despite changing external conditions.

How does Paramecium maintain homeostasis in freshwater?

It uses contractile vacuoles to expel excess water and maintain internal balance.

What is metabolism?

The sum of all chemical reactions occurring in an organism to maintain life.

Where do metabolic reactions occur in unicellular organisms?

In the cytoplasm, facilitated by enzymes.

How does Chlamydomonas utilize metabolism?

It captures sunlight with chloroplasts to produce glucose, which is then broken down for energy.

What is the difference between autotrophs and heterotrophs?

Autotrophs generate energy themselves (e.g., photosynthesis), while heterotrophs obtain energy by consuming others.

How do Paramecium and Chlamydomonas acquire nutrients?

Paramecium engulfs food particles through its oral groove, while Chlamydomonas absorbs light energy for photosynthesis.

What is the role of movement for unicellular organisms?

Movement helps them find food, avoid danger, and interact with their environment.

How does Paramecium move?

Paramecium uses cilia to propel itself.

How does Chlamydomonas move?

Chlamydomonas relies on flagella for swimming.

What is excretion?

Excretion is the removal of metabolic waste products from an organism.

How does Paramecium excrete waste?

Paramecium expels waste gases like carbon dioxide through diffusion across its plasma membrane.

What is the difference between excretion and egestion?

Excretion is the removal of metabolic waste, while egestion is the expulsion of undigested material.

How does growth occur in unicellular organisms?

Growth occurs as cells assimilate nutrients and synthesize new cellular material.

Why do many unicellular organisms divide when they reach a certain size?

Because their volume increases faster than their surface area, which can limit efficiency.

How do unicellular organisms respond to stimuli?

They detect and react to changes in their surroundings, such as moving toward light or reversing direction when encountering obstacles.

What is phototaxis?

Phototaxis is the movement toward light sources, as seen in Chlamydomonas.

What are the two types of reproduction in unicellular organisms?

Asexual reproduction (e.g., binary fission) and sexual reproduction (involving gamete fusion).

How does Paramecium reproduce asexually?

Through binary fission, where the cell divides into two identical offspring.

What is the significance of studying unicellular organisms?

They exemplify biological efficiency and provide insights into the fundamental principles of biology and the adaptability of life.