Placental Structure, Circulation, and Hormonal Function
Vascular Villi Organization
The vascular villi are formed by the smooth chorion and become individualized. Along the axes of these primitive villi, 25 to 50 daughter villi (free or hooked) develop for each primitive villus. Most reach the basal plate and are inserted into it.
The primitive villus hypertrophies, and its trunk is called the first-order villous stem. This stem gives rise to second-order villous stems, which divide in turn into third-order villous stems that adhere to the basal plate.
Read MoreMicrobiology Exam Review: Taxonomy, Viruses, and Fungi
Historical Shifts in Biological Taxonomy (1900–Present)
Significant changes in biological classification systems since 1900:
- The earliest change started with Carl von Nägeli in the 1800s, who proposed bacteria and fungi be placed in the Plant Kingdom. However, in 1959, they were given their own kingdoms.
- In 1937, the term prokaryote was introduced, and Robert G. E. Murray proposed the Kingdom Prokaryotae.
- In the 1960s, the molecular clock was proposed, establishing an evolutionary timeline based
Key Theories and Concepts in Evolutionary Biology
Foundational Theories of Species Change
Fixism: Species Stability Theory
Fixism is the theory that species were created following a predetermined pattern and, therefore, have always remained the same.
Key proponents include Georges Cuvier and Carl Linnaeus.
Evolutionism: Species Transformation
Evolutionism defends the idea that species have changed and transformed over time.
Key proponents include Jean-Baptiste Lamarck, Charles Darwin, and Alfred Wallace.
Key Figures and Contributions
- Georges Cuvier: Catastrophism.
Key Concepts in Biotechnology, Genomics, and Environmental Science
Biotechnology: Definition and Scope
Biotechnology is a science that integrates the natural sciences and engineering principles to implement organisms, cells, parts of cells, and their molecules in the development of useful products and services for human benefit. These products include pharmaceuticals like insulin or antibiotics.
Key Materials in Biotechnology
The essential working materials in biotechnology include:
- Restriction enzymes.
- Polymerase Chain Reaction (PCR) components.
Core Biotechnology Techniques
Key
Read MoreEcosystem Structure, Trophic Levels, and Energy Flow
Ecosystems and Trophic Relationships
Life takes place in the biosphere. The biosphere includes the atmosphere (specifically the troposphere), the entire hydrosphere, and the geosphere.
Defining Ecosystems
Contemplating a landscape, we can distinguish between living (biotic) and non-living (abiotic) components. These components are closely interrelated. The set of organisms and the relationships established between them constitute the ecosystem. Within an ecosystem, we distinguish:
- Biocenosis (or Community)
Human Circulatory and Lymphatic Systems: Structure and Function
The Internal Environment
The circulatory system is responsible for transporting nutrients to and from the cells in the body. It is made up of the heart, blood vessels, and blood.
Interstitial Fluid Renewal
Interstitial fluid is a liquid that surrounds the body’s cells. It must be renewed constantly (by the flow of blood, which adds nutrients and collects waste products) because:
- Cells consume nutrients from the interstitial fluid, and if it is not renewed, the nutrients would run out.
- Cells also release