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

Sexual Reproduction & Meiosis

Sexual Reproduction: Takes place when two sex cells, or gametes, from two parents of different sexes join together.

Meiosis: A cell division process through which haploid cells are formed.

Fundamental Genetic Concepts

• Traits: Each of the characteristics present in an organism that can be inherited by its offspring.
• Gene: A section of DNA that contains information about a certain trait and controls that trait.
• Alleles: Different forms of a gene.
• Homozygous: When two alleles for a specific trait are identical (e.g., AA, aa).
• Heterozygous: When two alleles for a specific trait are different (e.g., Aa).
• Genotype: An organism's complete set of genes.
• Phenotype: The observable way in which a genotype is expressed under specific

Trophic Levels

A trophic level consists of all organisms within an ecosystem that share the same feeding strategy.

Producers

Producers are autotrophic organisms that perform photosynthesis, using solar energy to convert inorganic matter into organic matter.

Consumers

Consumers are heterotrophic organisms that obtain energy by consuming other living organisms.

Primary Consumers

Primary consumers are herbivores that feed directly on producers.

Secondary Consumers

Secondary consumers are carnivores that feed on primary consumers.

Tertiary Consumers

Tertiary consumers (supercarnivores) are carnivores that feed on secondary consumers, such as lions.

Decomposers

Decomposers are heterotrophic organisms that break down dead organisms and waste products, returning... Continue reading "Ecosystem Dynamics: Trophic Levels, Food Chains, and Energy Flow" »

Cardiovascular System: Key Definitions

Cardiovascular Disease

It can be caused by smoking, poor diet, stress, physical inactivity, or hereditary factors.

Atherosclerosis

It is the hardening of artery walls caused by the buildup of cholesterol and lipids.

Hypertension

It is abnormally high blood pressure.

Heart Attack

It occurs when an artery that supplies blood to the heart becomes blocked.

Stroke

It occurs when a blood vessel in the brain becomes blocked or bursts.

Respiratory System Anatomy

The main parts of the respiratory system include:

• Nasal Cavities
• Mouth
• Pharynx
• Larynx
• Trachea (Windpipe)
• Bronchus
• Bronchiole
• Alveoli
• Lungs
• Diaphragm

Respiratory System Part Identification

1. It is the organ that produces the sense of smell: Nose/Nasal Cavity
2. It is also known as the

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

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" »

Essential Nutrients

Carbohydrates, proteins, and lipids are needed in significant amounts, while vitamins, minerals, and water are also crucial. Most foods are concentrated sources of one or two nutrients.

Food Groups

Foods are typically classified into five main groups:

• Grains
• Vegetables
• Fruits
• Milk
• Meat and Beans

Calories represent energy.

Carbohydrates

Carbohydrates provide us with ATP (energy).

• Two most important types: fructose (easy to absorb because it is a monosaccharide) and glucose (also a monosaccharide and the main carbohydrate in the blood).
• Other types: sucrose, maltose, and lactose. These are more difficult to absorb because they are disaccharides (two molecules linked).

Polysaccharides (Hard to Digest)

Polysaccharides are composed of many... Continue reading "Understanding Essential Nutrients" »

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