Notes, abstracts, papers, exams and problems of Biology

Allele Frequencies

Change in allele frequencies can be caused by:

• Natural selection
• Mutation
• Gene flow
• Genetic drift

Viral Reproduction

Steps of viral reproduction:

1. Attachment
2. Entry
3. Integration
4. Synthesis of viral components
5. Viral assembly
6. Release

Antibody Variable Regions

Primary function of the variable regions in antibodies: To bind specifically to antigens and determine the antibody's specificity.

Immunity

Innate Immunity

Innate (aka nonspecific) immunity is present at birth and functions the same way regardless of the pathogen. It involves:

• Phagocytosis
• Inflammation

In response to injury and/or pathogens, innate immune cells release paracrine signaling molecules such as cytokines and histamine that trigger inflammation. External pathogen features that can be... Continue reading "Biology Concepts Review" »

21)Signal Transduction is a process by which an extracellular signal molecule, called the first messenger activates a membrane receptor that in turn alters intracellular molecules, called the secondary messenger, to create a response.

Reproduction

We make new living beings similar to us. Men develop facial hair, deeper voices, more body hair, and bigger muscles. Women develop breasts, thicker lips, higher voices, and less body hair. The uterus is where the baby develops during pregnancy. Fallopian tubes connect the ovaries to the uterus. Ovaries contain the female sex cells, ova. The vagina connects the uterus to the outside of the body. The vulva is the external skin of the female reproductive system, which protects the opening of the vagina. The prostate gland produces a liquid that transports spermatozoa and provides them with nutrients, semen. The urethra is the tube that transports semen to the outside of the body. The penis is the organ that contains the urethra. Sperm... Continue reading "Human Reproduction: Anatomy and Process Explained" »

Understanding Aerobic Respiration

Aerobic respiration is a biological process that extracts energy from glucose and other organic compounds to create adenosine triphosphate (ATP) using oxygen.

The Four Stages of Aerobic Respiration

1. Glycolysis

   • Occurs in the cytoplasm.
   • A six-carbon glucose molecule is converted into two, three-carbon molecules of pyruvate.
   • This process occurs in the cytoplasm.
   • To initiate the process, two molecules of ATP are consumed. Four molecules of ATP and two molecules of NADH are produced.

2. Formation of Acetyl Coenzyme A

   • Involves shuttling pyruvate molecules into the mitochondrion.
   • Each pyruvate molecule is oxidized to carbon dioxide and a two-carbon acetyl group.
   • The carbon dioxide is released as a waste product, and the two-carbon

1. What are plant hormones?

Answer

Plant hormones are fluids secreted within the plant, also known as phytohormones. They regulate the growth and development of the plant. Examples of plant hormones are auxin and gibberellins.

2. How is the movement of leaves of the sensitive plant different from the movement of a shoot towards light?

Answer

The movements of the leaves of the sensitive plant are touch-sensitive and independent of growth, while the movement of the shoot towards light is growth-related and known as phototropism.

3. Give an example of a plant hormone that promotes growth.

► Auxin

4. How do auxins promote the growth of a tendril around a support?

Answer

When tendrils come in contact with any support, the part of the tendril in contact... Continue reading "Plant Hormones and Reflex Actions: Questions and Answers" »

Ecosystem Dynamics

An Ecosystem is a system formed by a group of organisms of different species or Biocenosis, the environment in which they live, and its physical and chemical characteristics or Biotope and the Interactions that are established between them.

Environmental factors are all the components of the ecosystem that have an Impact on the Biocenosis through their Presence or Variation.

Environmental factors determine:

• Distribution and Composition of the Biocenosis: the type and number of populations that make it up.
• How many organisms are present in each population.
• The Adaptations the organisms exhibit.

Types of Environmental Factors

Abiotic Factors

Are the Physical and Chemical components of an ecosystem, their variation, modifies the life... Continue reading "Ecosystem Dynamics: Biotic and Abiotic Factors" »

TROPHIC LEVEL = consists of all the organims in an ecosystem which obtain their food in the same way.

Cellular Transport and Water Potential

Diffusion

The movement of molecules from an area of high concentration to an area of low concentration through a partially permeable membrane. (Osmosis is the same but with water molecules)

Concentration Gradient

The difference in concentration of a substance between two different areas.

Active Transport

The uptake of particles by cells against a concentration gradient. It requires energy and a carrier protein.

Partially Permeable Membrane

A membrane that allows small molecules of water and certain solutes but does not allow the passage of large solute molecules.

Kinetic Energy

The energy of movement

Brownian Motion

The random movement of particles

Water Potential

The ability for a substance or cell to accept more water.... Continue reading "Understanding Key Concepts in Biology and Physics: Diffusion, Energy, and Heat Transfer" »

1. What kind of organelles do photosynthetic Protista contain?

• Multicellular and Unicellular

2. The main body of Fungi is called?

• Mycelium

3. Plants produce ________ for our survival

• Oxygen

4. What are the 2 transport plant tissues called?

• Xylem and Phloem

5. What is the smallest group of Bryophytes?

• Hornworts

6. A plant with a fibrous root system and leaves with parallel venation would also have?

• None of the above

7. Where does pollen transfer on plants to start reproduction?

• Stigma

8. If a farmer wanted a more loosely packed cluster of grapes, he would most likely spray the immature bunches with?

• Gibberellins

9. Who formulated for the first time the Theory of evolution?

• Lamarck

10. What is not inferred from Darwin's Theory?

• None of the above

11. What is the... Continue reading "Biology Quiz: Organisms and Their Characteristics" »

Infectious Diseases: An Overview

Changes to body physiology that disrupt normal body functions and are caused by microorganisms are called infectious diseases. This explanation, established by Louis Pasteur and Robert Koch, is called the germ theory of disease.

Causes of Infectious Diseases

Infectious diseases are caused by various microorganisms, including:

• Viruses
• Bacteria
• Fungi
• Protists
• Parasitic worms

Disease-causing microorganisms are also called pathogens. Koch also developed a series of rules, known as Koch's postulates, that help scientists identify which organism causes a specific disease.

While many microorganisms are symbionts that are either harmless or beneficial, pathogens cause disease by:

• Destroying cells
• Disrupting body functions
• Releasing