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

Arthropod Characteristics: Defining Features

Arthropods are defined by the following characteristics:

• Segmented body structure
• Coelomate (possessing a true coelom)
• Invertebrate
• Bilateral symmetry
• Exoskeleton with jointed appendages

Arthropods were the earliest known invertebrates to have jointed appendages, which allows for flexibility despite having a hard exoskeleton.

The Arthropod Exoskeleton

The exoskeleton is a hard, outer covering made of chitin and protein.

Functions of the Exoskeleton

• Protects and supports internal structures.
• Allows for the attachment of muscles.

Molting

Exoskeletons cannot grow, so they must be replaced throughout life, a process known as molting.

Body Segmentation

Most arthropods exhibit three primary segments: the head, thorax,... Continue reading "Defining Arthropod Characteristics and Body Systems" »

Characteristics of Poriferans

Poriferans, also called sponges, are aquatic organisms (the majority of them are marine organisms) that either have no symmetry or have radial symmetry. Their bodies, which have a tube shape, a cup shape, or an irregular shape, have multiple pores that are interlinked by thin channels. These channels lead to a central cavity, called the atrium, which is linked to the outside by an opening called the osculum. Inside the channels, there are cells known as choanocytes, which are specialized in capturing food.

Poriferans stay upright due to a skeleton made of small spines called spicules. They feed by filtration. Water, which contains food particles, enters through the pores and exits through the osculum with the food... Continue reading "Characteristics of Poriferans: Aquatic Organisms with Unique Structures and Reproduction" »

Microorganisms and Diseases

Microorganisms and associated diseases:

• Viruses: Common cold
• Bacteria: Pneumonia
• Protozoa: Malaria
• Fungi: Athlete's foot

Infectious Disease Transmission

Methods of infectious disease transmission:

• Waterborne: Cholera
• Vector-borne: Malaria
• Foodborne: Salmonella
• Airborne: Influenza (the flu)

Types of Diseases

Infectious Diseases: Influenza, AIDS, Gonorrhea, Tetanus, Measles, Tuberculosis

Non-Infectious Diseases: Diabetes, Lung cancer, Heart attack, Alzheimer's disease, Arthritis

Infections and Defenses

Infections and the body's defenses:

• Infected wound: Skin
• Intestinal infection: Large intestine
• Respiratory infection: Respiratory tract
• Vaginal infection: Bladder

Sexually Transmitted Diseases (STDs)

Three common sexually transmitted diseases:... Continue reading "Human Biology: Microorganisms, Diseases, and Reproduction" »

Human Body Organization

The human body is structured in a hierarchical manner, from the smallest components to the entire organism and its interactions within an ecosystem.

1. Subatomic Level

Consists of subatomic particles, i.e., protons, electrons, and neutrons (and sub-particles like quarks and leptons).

2. Atomic Level

Formed by atoms, the bioelements found in living beings. These include:

• Primary Bioelements: Essential for forming organic biomolecules (C, H, O, N, P, S), constituting 96% of dry living matter.
• Secondary Bioelements: Constitute 3% of dry living matter.
• Trace Elements: Present in small amounts but crucial for health (e.g., iron, iodine).

3. Molecular Level

Molecules are formed by grouping two or more atoms. Biomolecules in living beings... Continue reading "Human Body Organization: From Atoms to Ecosystems & Cell Basics" »

Genetic Code

• Each codon or triplet codes for a specific amino acid.
• It is degenerate: Amino acids can be coded by more than one codon or triplet (some triplets are synonyms). There are 64 codons for 20 amino acids.
• It is not ambiguous: Each codon encodes only one type of amino acid.
• It is universal: Apart from a few small exceptions.
• There are triplets that determine the beginning of translation ('start codon'): AUG (It codes for the amino acid methionine - Met).
• There are triplets that determine the end of translation ('termination' or 'stop' codons): UAA, UAG, UGA (They do not code for any amino acids).

Chromosomes

They are stick-shaped structures that arise from the condensation and packaging of chromatin during the division phases (mitosis and... Continue reading "Key Concepts: Genetic Code, Chromosomes, DNA, Cell Cycle" »

1)Which of the following best describes a karyotype?

·a display of each of the chromosomes of a single cell

2) The human X and Y chromosomes

·include genes that determine an individual's sex.

3) Which of the following is true of a species that has a chromosome number of 2n = 16?

·Each cell has eight homologous pairs.

4) In a human karyotype, chromosomes are arranged in 23 pairs. If we choose one of these pairs, such as pair 14, which of the following do the two chromosomes of the pair have in common?

·Length, centromere position, staining pattern, and traits coded for by their genes.

5) Meiosis II is similar to mitosis in that

·sister chromatids separate during anaphase

6) Which of the following occurs in meiosis but not in mitosis?

·synapsis of... Continue reading "Understanding Genetics: Karyotypes, Meiosis, and Inheritance" »

Difference between primary and secondary sex characteristics:

The primary are the sexual organs which are born with and the secondary are the physical characteristics developed during puberty

Reproduction:

Reproduction is the creation of new individuals

Explain the journey of sperm to the ovum:

After being secreted by the penis through the urethra, the sperm go from the vagina to the uterus. Then, they divide into 2 groups and go to each fallopian tube. If there’s an ovum, one of these single sperm will fertilize it, and they will form a zygote, divide and become a morula and later a blastocyst. On the 7th day, the blastocyst implants in the endometrium

Structure:

Pathogenic Eukaryotes

Protozoa: Characteristics and Diseases

This section describes the diseases caused, modes of locomotion, trophozoite/cyst stages, and infective and diagnostic stages for the following protozoan parasites:

• Entamoeba histolytica: Trophozoites and Cysts

  • Locomotion: This protozoan moves with the help of pseudopods (false feet).
  • Stages: The trophozoite form has a single nucleus, while the cyst contains a maximum of four nuclei and is typically round.
  • Infection & Development: During ingestion, the cell wall of a mature quadrinucleated cyst disintegrates, and its nuclei divide, producing eight active trophozoites. These trophozoites move to the colon, where they establish infection.
  • Trophozoite Morphology: Trophozoites are variable