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

How does Fixism explain the diversity of living things?

(4 marks) Fixism claims that species were created the way they are now, given that they do not change. Therefore, the diversity we find today is the diversity that has always existed. c.

Explain why two very different species such as birds and butterflies can have similar wings, responsible for the same function. Which evidence of evolution is it? (4 marks)

Given that both species must adapt to the same environment, they end up developing similar structures. It is an example of convergent evolution.

According to Darwin, why do individuals compete against each other? What are the consequences of this constant competition? (4 marks)

The cause is the lack of resources in an environment and the... Continue reading "Explaining Diversity of Living Things: Fixism, Evolution, and Ecological Factors" »

Eyes

Orbital Hematoma (Black Eye)

An orbital hematoma, commonly known as a black eye, results from a blow to the area surrounding the eye, which causes capillary bleeding.

Signs & Symptoms:

• Noticeable swelling and discoloration around the orbit.

Orbital Fracture

An orbital fracture is caused by a direct blow to the eyeball, forcing it posteriorly. This action compresses the orbital fat until a blowout rupture occurs to the floor of the orbit.

Signs & Symptoms:

• Diplopia (double vision)
• Restricted eye movement
• Downward displacement of the eye

Hyphema

A hyphema is a collection of blood in the anterior chamber of the eye, typically resulting from blunt trauma to the eye. This is a major eye injury that can lead to serious problems.

Signs & Symptoms:

The Nervous System

Cranial Nerves

Twelve pairs of cranial nerves enter and exit the brain, comprising sensory, motor, and mixed types. They innervate the head, upper torso, and some internal organs. Some cranial nerves are associated with the autonomic nervous system. Along their pathways, ganglia—groups of neuronal cell bodies—can be observed.

Spinal Nerves

Thirty-one pairs of mixed spinal nerves emerge from the spinal cord. Each nerve originates as two distinct roots—dorsal and ventral—which merge to form a single nerve cord. Sensory neurons enter the spinal cord through the dorsal root, while motor neurons exit through the ventral root.

The Autonomic Nervous System

The autonomic nervous system (ANS) regulates involuntary bodily functions.... Continue reading "The Nervous and Endocrine Systems: A Comprehensive Overview" »

Special diets:

-Low cholesterol diet

-Low salt diet

-Gluten free diet

-Diabetes diet

-High or low calorie diets

Excretion:Is the process of

eliminating or expelling waste

matter from our bodys.

Excretion of CO2: Carbon

dioxide is produced during

cellular respiration and is

excreted from the body by

the lungs.

Wastes that are solids:The urine

and the sweat.

The urine:This is usually yellow

or transparent , but it can be

opaque when there is a lot of

waste. More or less the 95% is

water and the other 5% are

dissolved substances .The

composition is similar to blood

plasma .Urea is the primary

waste molecule in the urine .

Sweat:Is similar to urine but is

more dilute , approximately 99%

water.

sweat glands.The tiny , tubular

structures within the skin expel

Human Beings and Health

The World Health Organisation (WHO) defines health as 'the complete physical, mental and social well-being, not only the absence of disease'.

Factors that Influence Health

The environment: healthy surroundings should be free of biological, physical or chemical elements that are harmful to your health.
Personal characteristics: genetic factors, age and gender predispose people to suffer from certain types of illnesses.
Lifestyle: healthy habits and lifestyles are very important for staying healthy.
Healthcare: it is essential to have an efficient healthcare system to guarantee public health.

Vital Signs

Vital signs are physiological parameters that inform us of our state of health or the evolution of a disease.

White Matter:

Formed by neurons' axons, white matter acts as communication cables and the connection between control centers.

Brain:

Part of the central nervous system found within the cranium, the brain weighs 1.4kg and is the largest organ in our body. It serves as the center of integration and consciousness. The brain is organized with grey matter making up the outer surface and white matter in the interior. Cranial nerves emerge directly from the brain, which is part of the peripheral nervous system.

Parts of the Brain:

• Cerebellum:

  The largest part of the brain, consisting of hemispheres, the corpus callosum, the hippocampus, the thalamus, and the hypothalamus.

• Hypothalamus:

  The master gland of the endocrine system, controlling most of its activity.

Question 1:

Group the following as nitrogenous bases and nucleosides:

• Adenine, Cytidine, Thymine, Guanosine, Uracil and Cytosine.

Answer

Nitrogenous bases present in the list are adenine, thymine, uracil, and cytosine.

Nucleosides present in the list are cytidine and guanosine.

Question 2:

If a double stranded DNA has 20 per cent of cytosine, calculate the per cent of adenine in the DNA.

Answer

According to Chargaff’s rule, the DNA molecule should have an equal ratio of pyrimidine (cytosine and thymine) and purine (adenine and guanine). It means that the number of adenine molecules is equal to thymine molecules and the number of guanine molecules is equal to cytosine molecules.

% A = % T and % G = % C

If dsDNA has 20% of cytosine, then according to... Continue reading "Understanding DNA: Bases, Replication, and Functions" »

Genetics: Key Concepts

Vocabulary Terms:

• Chromosome: A structure of nucleic acids and protein found in the nucleus of most living cells, carrying genetic information in the form of genes.
• Gene: A unit of heredity transferred from parent to offspring, determining some of the offspring's characteristics.
• Homologous Pairs: Chromosomes containing genes for the same traits but potentially different alleles. These are usually paired during mitosis.
• Allele: One of two or more alternative forms of a gene that arise by mutation and are found at the same location on a chromosome.
• Sister Chromatid: Identical copies of a chromosome formed by DNA replication, joined by a common centromere. It's essentially half of a duplicated chromosome.
• Nucleotide: A compound

• The outer ear: it is formed by the pinna and the auditory canal.
• The middle ear: a cavity in the eardrum that reaches the oval window and the round window.
• The inner ear: formed by the membranous labyrinth.
• Sweat gland: this secretes sweat, cooling the body surface when it is necessary and removing certain waste substances.
• Sebaceous gland: these secretes substances that lubricate the skin and hair.
• Taste buds: are located inside the mouth especially on the tongue.
• Long bones: these are long and contain spongy bone tissue at either end, as well as compact bone.
• Short bones: these are rounded and mostly made up of spongy bone tissue.
• Flat bones: these are plate-shaped. Formed by an inner layer of bone tissue surrounded by two layers of compact bone