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

Mitosis: Cell Division for Growth

1. Interphase: DNA and centrosomes have been duplicated.
2. Prophase: The nuclear membrane disappears, chromosomes condense and become visible, and the spindle apparatus begins to form from proteins.
3. Metaphase: The centrioles are at opposite poles of the cell. The spindle fibers align the chromosomes at the cell's equator (metaphase plate).
4. Anaphase: The spindle fibers pull the sister chromatids of each chromosome toward opposite centrosomes.
5. Telophase: The chromatids decondense back into chromatin. New nuclear membranes form around the chromatin, and the spindle breaks down.
6. Cytokinesis: The cytoplasm is divided, forming two new, genetically identical daughter cells.

Meiosis: Producing Gametes

Interphase: DNA and centrosomes... Continue reading "Mitosis vs Meiosis: Understanding Cell Division Processes" »

What is Animal Cloning?

Cloning is the process by which we obtain an identical copy, or clone, from the genetic point of view of any living entity, such as a cell or an organism.

How Do You Clone an Animal?

The first time that clone cells were obtained from an adult animal was in 1996. As a result, the sheep Dolly was born, the first mammal cloned in history. The technique used is called nuclear transfer.

Stages of Animal Cloning

1. A differentiated cell is taken from the individual that is to be cloned. These cells contain the entire genome of the organism, with the difference that it is a specialized cell that has lost the ability to reproduce.
2. An egg is taken from a female donor.
3. The egg nucleus is removed.
4. The nucleus of the differentiated cell is

Essential Food Groups and Nutritional Components

Food groups are categorized by their primary nutritional contributions:

• Milk, Milk Derivatives, and Eggs

  Source of proteins, vitamins, and calcium.

• Meat, Poultry, and Fish

  Primarily provide protein.

• Fats and Oils

  Include animal fats (e.g., butter) and vegetable oils. They provide lipids needed when eaten in moderation.

• Cereals, Pulses, Potatoes, and Sugar

  Provide proteins and glucids (carbohydrates).

• Vegetables

  Source of vitamins and fiber.

• Fruit

  Provide glucids (carbohydrates), vitamins, and fiber.

Macronutrients: Energy and Building Blocks

• Glucids (Carbohydrates): Provide energy. Most common forms are starches (found in pulses and potatoes) and sugars (e.g., glucose).
• Fibre: A type of glucid derived from vegetables.

Sensory Perception and Bodily Responses

Sensory Perception

Sensory perception is the process of obtaining information through our senses: sight, hearing, balance, smell, taste, and touch. Receptors also exist that capture the internal conditions within the body.

Bodily Responses

Our body's responses are executed by the locomotor system (formed by bones and muscles) and the endocrine system (which functions through hormones), responsible for movement and regulation.

The Sense of Sight (Vision)

Key components of the eye include:

• Cornea: A transparent layer that covers the front of the eye.
• Iris: A layer that can dilate or shrink, regulating the passage of light through an opening called the pupil.
• Sclera: The layer that gives shape to the eyeball.
• Conjunctiva:

Key Ecological Concepts

Ecology is the science that studies the relationships between living beings, and also between them and their surrounding environment.

• Population: A group of individuals of the same species living together in a given area.
• Community: A group of populations living together in a specific area.
• Biotope: The physical environment or habitat occupied by a community.
• Ecosystem: The combination of the community and the biotope in which they live, including the ways in which individuals interact with one another and with their surrounding environment to reproduce and form a stable system.

Environmental Factors

The environment is influenced by various factors:

• Biotic factors: Factors that result from the presence and activities of other

Polymerase Chain Reaction (PCR)

Continuous replication is a fragment of DNA containing a gene or genes of our interest. In this way, we obtain a large number of copies that make it possible to study without worrying about the amount of the sample.

At first, it was a cumbersome technique. Due to the different temperatures used during the process, some of them very high, we were forced to replace the polymerase at each change in temperature. This problem was solved by the DNA polymerase of a thermophilic bacterium: Thermus aquaticus (Taq polymerase).

The method is deceptively simple and involves replication in a medium rich in triphosphate nucleotides, the DNA strand of interest, to which we add small pieces of RNA and Taq polymerase.

A cyclic temperature

Eukaryotic Cell Organelles and Functions

Eukaryotic cells, found in animals, plants, fungi, and protists, contain specialized structures called organelles that perform essential life functions. Below is a detailed look at the key components found in animal and plant cells.

Animal Cell Organelles

Nucleus: The Control Center

• Nickname: The Control Center
• Function: Holds the DNA (genetic material).
• Parts: The Nucleolus is the dark spot within the nucleus that helps manufacture ribosomes.

Ribosomes

• Function: Responsible for protein synthesis (making proteins).
• Note: Ribosomes are found in all cells, both Prokaryotic and Eukaryotic.

Endoplasmic Reticulum (ER): The Roads

• Nickname: Roads (Internal Delivery System)
• Function: Serves as the internal delivery system

Human Digestive and Circulatory Systems

Nutrition is the process by which a living being obtains the matter and energy needed to sustain life.

Components of Digestive Function:

• Taste: Involves eating food, breaking it down, and transporting it.
• Reduce: Food is broken down into simple molecules that cells can use.
• Absorb: Simple molecules are absorbed and passed into the bloodstream for circulation to all body tissues.
• Remove: Undigestible remains are eliminated.

Digestive Tract Components:

The Pharynx

A short part of the digestive tract, also part of the respiratory system, extending from the oral cavity to the top of the esophagus.

The Esophagus

The conduit between the pharynx and the stomach.

The Stomach

An enlarged, bag-shaped part of the digestive tube,... Continue reading "Human Digestive and Circulatory Systems: Functions and Components" »

The Digestive Process

There are three phases in food processing: digestion, absorption, and the expulsion of waste. The movement of food through the digestive tract is known as peristaltic movements. These consist of the narrowing of the tube through the contraction of the muscles of the walls. The muscles contract successively.

Digestion

Types of Digestion

• Mechanical digestion consists of cutting, crushing, moving, and diluting foods.
• Chemical digestion is done through the action of various substances, which attack the foods and bring about chemical changes.

Stages of Food Digestion

• Digestion in the mouth is a result of mastication and salivation. Mastication cuts and crushes the food. Saliva is a liquid produced by the salivary glands in the mouth.

Female Reproductive Tract: Anatomy and Function

• Oviducts (Fallopian Tubes or Uterine Tubes)

  These are two small tubes with a funnel-shaped opening at the end closest to the ovaries. They are responsible for collecting the eggs released by these organs. Fertilization occurs in the fallopian tubes. The innermost layer of these tubes consists of ciliated cells that enable the movement of the eggs along them. They also secrete a fluid that facilitates the movement of the zygote before it reaches the uterus.

• Uterus

  A conical-shaped cavity into which the fallopian tubes lead. Its wall has a thick muscular layer, the myometrium, and is lined internally by a mucous layer, the uterine lining (endometrium). At its lower end, called the neck or cervix, the