Biological Evolution and the Diversity of Life
Evolution and Natural Selection
Evolution is the gradual and continuous accumulation of heritable changes in populations that give rise to new species.
Fixism
This theory holds that species remain fixed and immutable from the beginning to the present day. Fixist theories are strongly influenced by myths and religious beliefs.
Main Fixists
- Linnaeus grouped organisms according to their degree of similarity.
- Cuvier, a French anatomist, was a defender of fixist theories. To explain the existence of fossils,
Skeletal Muscle Structure, Function, and Nervous System Integration
Functions of the Skeletal System
- Move the body
- Maintain posture
- Protect and support
- Regulate elimination of materials
- Produce heat
Characteristics of Skeletal Muscle
- Excitability: Ability to respond to a stimulus by changing electrical membrane potential
- Conductivity: Sending an electrical change down the length of the cell membrane
- Contractility: Enables movement when filaments slide past one another
- Extensibility: Ability to stretch
- Elasticity: Ability to return to original length after shortening or lengthening
Muscle
Read MoreUnderstanding Human Nutrition and Metabolism
What is Nutrition?
Nutrition is the process by which cells incorporate elements and perform nutritional functions. Cells are grouped in the following way: cells associate to form organs, organs coordinate to form systems, and systems cooperate to allow your body to function, think, work, and play.
Metabolism: A Series of Chemical Reactions
Metabolism includes anabolism (building tissues like muscle, bone, and blood) and catabolism (breaking down substances and tissues).
Food provides fuel for these
Read MoreHuman Respiratory System: Function and Anatomy
Respiratory System: Function and Anatomy
Function: Exchange of gases between the body and the atmosphere.
Human respiratory, or pulmonary, respiration consists of:
Driving System
Nostrils, mouth, pharynx, larynx, trachea, bronchi (main, lobar, segmental), and bronchioles.
Exchange System
Alveolar tubes and sacs. The anatomic dead space, or respiratory zone (no gas exchange) of the bronchial tree, includes the first 16 bronchial generations, and its volume is 150 ml.
The respiratory function is to move
Read MoreEvolution and Human Origins: A Comprehensive Study
Evolution: Key Concepts and Evidence
Neutral Theory of Molecular Evolution
Independent: The Japanese scientist Motoo Kimura suggested that most mutations that occur during evolution are neutral, indifferent to natural selection. For the same reason, their distribution in a population corresponds to a purely random factor. According to the neutral theory, natural selection is not pure chance but allows for several populations in which a particular mutated gene can be dispersed without any selective
Read MoreDNA Structure, Function, and Genetic Code
DNA: Structure and Characteristics
1) DNA is composed of two chains coiled together to form a double helix.
2) Each chain is made up of units called nucleotides. In DNA, there are four types of nucleotides: Adenine (A), Guanine (G), Cytosine (C), and Thymine (T). Each nucleotide consists of a phosphate, a deoxyribose sugar, and a nitrogenous base.
3) The two chains are united through their nucleotides in the following way: adenine binds to thymine (A-T), and guanine binds to cytosine (G-C). The number
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