Notes, summaries, assignments, exams, and problems for Biology

Redi's Experiment
1668, Francesco Redi demonstrated that the maggots found in rotting meat came from fly’s eggs
1.     Redi placed pieces of meat in the same jars
2.     The first he left open, the second one he covered with some fabric and the third he covered with a cork
3.     The three jars were left in the same place and after a few days he saw that there were maggots in the first two jars but not the third one

Pasteur’s Experiment
Louis Pasteur demonstrated that microorganisms were not created from spontaneous generation.
1.     Pasteur placed meat soup in two flasks and bent their neck into an S-shape
2.     He sterilised the liquid by heating it and after two weeks saw that it didn’t decompose
3.     He

Stage B: The Digestion Process

Digestion is the second stage of the digestive process, where food is transformed into nutrients that the body can absorb.

Digestion primarily takes place in the stomach (a large cavity in the digestive tract with muscular walls) and the first portion of the small intestine, the duodenum.

Steps of Digestion

1. The bolus reaches the stomach, entering through the cardiac sphincter (the entrance door of the stomach). This sphincter acts as a double-way door.
2. Once in the stomach, the bolus is mixed with two substances secreted by the stomach walls:
   • Pepsin: An enzyme used to break down proteins.
   • Hydrochloric Acid (HCl): Lowers the pH to activate pepsin and destroy pathogens.

   This mixing process is aided by the movements of the

Vertebrata

Vertebrates are characterized by a backbone created from small parts called vertebrae and an endoskeleton. The endoskeleton can be made of:

• Cartilage (Cyclostomata, Chondrichthyes)
• Bones (Osteichthyes, Amphibians, Reptiles)

Key systems include:

• Central Nervous System: Brain, spinal cord, peripheral nerves forming a tubular nervous system.
• Vascular System: Closed, chambered heart.
• Breathing System: Gills, lungs.
• Excretory System: Kidneys.

They mostly have four limbs, although these are sometimes modified (e.g., fish fins, bird wings) or absent (e.g., snakes).

Cyclostomata (Jawless Fish)

These animals lived on Earth 500 million years ago. They live in shallow seas, mild climatic areas, and sometimes in fresh water. Their mouth opening is round;... Continue reading "Vertebrate Animal Groups and Features" »

Transport of Macromolecules

Exocytosis: Secretion and Excretion

Exocytosis involves the flow of vesicles leaving the Golgi apparatus and moving toward the cell membrane.

• Constitutive: A continuous flow leaving the Golgi apparatus.
• Inducted: Found in cells specialized in secretory processes.

Pathway: Endoplasmic reticulum → Golgi → Membrane.

Endocytosis: Cellular Ingestion

Endocytosis is the ingestion of substances by vesicles formed within the cell membrane.

• Phagocytosis: Ingestion of large particles by specialized cells called phagocytes.
• Pinocytosis: Ingestion of substances dissolved in small liquid drops that traverse the cell membrane, forming small pinocytic vesicles.
• Receptor-Mediated Endocytosis: Macromolecules bind to transmembrane receptor

Functions of the Endocrine System

The endocrine system performs several vital roles in maintaining the body's internal environment. Its most important functions include:

• Reproduction
• Metabolism and Energy Balance
• Growth and Development
• Body Defenses
• General Homeostasis: Maintaining water, nutrient, and salt balance in the blood.

While all are critical, homeostasis is often considered the most important as it ensures a stable internal environment for all other processes.

Major Endocrine Glands and Their Hormones

The following table details the primary endocrine glands, the hormones they secrete, and their specific functions:

Cell Theory

Cells are the basic unit of life, all organisms are made up of 1 or more cells, and all cells arise from existing cells.

Contributors to Cell Theory

Hooke

Robert Hooke, a British scientist, first named cells in 1665. He observed cork with a microscope.

Scheiden

Matthias Jakob Schleiden, a German botanist, concluded that plants were made of cells.

Schwann

Theodor Schwann, a German zoologist, found that all living things are made of cells.

Leeuwenhoek

Antonie van Leeuwenhoek, a Dutch fabric store owner, ground a lens that magnified the microscope 200x's.

Virchow

Rudolf Virchow, a German doctor, disputed the idea of spontaneous generation (the idea that cells come from nothing) and concluded that cells come from other cells.

Cell Structures

Cell

Food and Nutrients

Food is our primary source of nutrients. But what are nutrients exactly?

Nutrients: The Essentials for Life

NUTRIENTS are biomolecules that our bodies need to sustain vital functions. They are the chemical components of food, acting as the building blocks and energy sources our cells need to survive.

Why We Need Nutrients

Cells require nutrients to fulfill three fundamental requirements:

1. Energetic: Certain nutrients, like lipids and carbohydrates, are broken down in our mitochondria to release energy. This energy powers essential functions such as movement, temperature regulation, and more.
2. Structural: Some nutrients, including proteins, lipids, and mineral salts, serve as the building blocks for various body structures. These structures

Life Processes

Life processes are the processes that are necessary for an organism to stay alive. Examples include nutrition and respiration.

Criteria of Life

• Growth
• Movement

Nutrition

Nutrition is the process in which an organism takes in food, utilizes it to get energy for growth, repair, maintenance, etc., and excretes the waste materials from the body.

Types of Nutrition

1. Autotrophic Nutrition

(Auto = self; trophos = nourishment) Examples: Plants, Algae, Blue-green bacteria.

• Process: Photosynthesis (Photo = light; Synthesis = to combine)
• Raw Materials:
  • Carbon dioxide
  • Water
• Energy Conversion: Light/Solar energy to Chemical energy
• Role of Chlorophyll: To trap the sun's energy for photosynthesis
• Factors for Autotrophic Nutrition:
  • Carbon dioxide
  • Water
  • Light
  • Temperature
• Events/

Cellular Interaction and Responses

Cellular interaction is the capacity of cells to detect changes in their environment and respond to them correctly.

Types of Cellular Responses

Static Response

In a static response, there is no movement produced. Rather, the cell responds in a different way, for example, by secreting a substance.

Dynamic Response (Taxis)

In a dynamic response, the cell responds by moving. These movements are collectively called taxis (plural: taxa). They are considered:

• Positive: If the cell moves towards the stimulus.
• Negative: If the cell moves away from the stimulus.

Mechanisms of Cellular Movement

Flagellar and Ciliary Movement

This type of movement is produced in cells that have cilia (many tiny structures) or flagella (longer than... Continue reading "Cellular Responses, Movement, and Reproduction Mechanisms" »