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Darwin's Observation (Fossils, Galapagos Islands & Africa ) and Natural Selection (Adaptive Traits)

By: HWC, Views: 7637

Along Darwin's voyage, he made many observations. Each one added to his understanding of how organisms change over time. Darwin was already familiar with fossils and knew that many fossils were very different from living organisms. But, also there were some fossils that were very similar to li...

Natural Selection, Species Isolation and Real World Example

By: HWC, Views: 7175

`Natural selection' is the process in which organisms with adaptive traits survive and breed in greater number than organisms without such traits. Eventually, almost all of the individuals in the population will have the same adaptive trait. This was the concept presented by Charles Darwin in ...

DNA Replication Factory and Protein

By: HWC, Views: 7256

DNA (deoxyribose nucleic acid) carries all the genetic information needed to re-create itself and to pass on the characteristics of the organism. The “factory” model of DNA replication hypothesizes a specific nuclear structure in which the molecular machinery for replication forks are brou...

New DNA Strand Replication

By: HWC, Views: 7146

First step: strands are separated • Helicase unwinds the DNA double helix at the replication fork • SSBs coat the single strands to prevent reannealing • Polymerase attaches nucleotide at 3' end • Synthesis is in 5' to 3' direction DNA Polymerase: • Only extends nucleic ac...

The Lagging Strand in DNA Replication and Replication in Action

By: HWC, Views: 7238

The lagging strand is the strand of nascent DNA whose direction of synthesis is opposite to the direction of the growing replication fork. DNA backbones run in opposite directions, the strands in a DNA molecule are oriented antiparallel to one another. New DNA is made by enzymes called DNA...

Cavernous Sinus Larynx Middle Ear Orbit: Granulesm Animation

By: HWC, Views: 7193

The cavernous sinuses are located within the middle cranial fossa, on either side of the sella turcica of the sphenoid bone (which contains the pituitary gland). The cavernous sinuses, a rich plexuses of veins that surround the internal carotid arteries, lie lateral to the pituitary fossa. Ant...

Photosynthesis and Van Helmont Experiment

By: HWC, Views: 7004

All energy on Earth comes from a star, the Sun. Light must travel 160 million kilometers to reach Earth where plants capture this light energy and convert it to chemical energy in the form of sugars. This biochemical process is called PHOTOSYNTHESIS. The summary equation for photosynthesis is ...

Electromagnetic Spectrum, Chlorophyll and Pigment & Light

By: HWC, Views: 7521

The sun gives off radiation that is called the electromagnetic spectrum. This is energy that travels as wavelengths and includes radio waves, X-rays and ultraviolet light. A portion of this radiation is known as visible light, and is the type of radiation that plants use to manufacture sugars. ...

Chloroplast Structure & Light Dependent Reactions (Photosystem 1 and 2 Cyclic Electron Flow)

By: HWC, Views: 7325

The leaf is the principle photosynthetic organ of the plant. This is a cross section of a leaf. The rectangular-shaped cells are part of the photosynthetic tissue called the palisade mesophyll. Each photosynthetic cell can contain several hundred organelles known as chloroplasts. The chlorop...