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Metabolic Rate, Heat and Thermoregulation - response to heat and cold stresses

By: HWC, Views: 6880

• A neuron group in the anterior portion of the hypothalamus controls heat balance. • Neurons in the preoptic region of the hypothalamus integrate signals that come from thermoreceptors. • The temperature control center in the preoptic region propagates control signals to two other part...

Egg and Sperm Formations in Animals Animation

By: HWC, Views: 560

Inside the ovaries of a female animal are diploid germ cells called oogonia. An oogonium grows to become a primary oocyte. This large cell is still diploid. Meiosis I followed by unequal cytoplasmic division produces one large secondary oocyte and a smaller polar body. Both are haploid. ...

Ciliate conjugation Animation

By: HWC, Views: 1039

Protozoan conjugation is an unusual form of sexual reproduction Prospective partners join together, usually at the surface of their oral depressions. The cells undergo cytoplasmic fusion. Meiosis II produces four haploid micronuclei. Now the macronucleus of each cell begins to bre...

Introduction to Genetics

By: Administrator, Views: 9515

Genetics is a branch of biology concerned with the study of genes, genetic variation, and heredity in organisms. Gregor Mendel, a scientist and Augustinian friar, discovered genetics in the late 19th-century. Mendel studied "trait inheritance", patterns in the way traits are handed down from p...

Spermatogenesis Animation

By: Administrator, Views: 9945

Spermatogenesis is the process by which haploid spermatozoa develop from germ cells in the seminiferous tubules of the testis. This process starts with the mitotic division of the stem cells located close to the basement membrane of the tubules. These cells are called spermatogonial stem cells. T...

Endocytosis -Types and Phagocytosis

By: HWC, Views: 6693

Endocytosis is the process by which a substance is brought inside a cell without having to pass through the cell membrane. It is the opposite of endocytosis, the process by which substances exit the cell without having to pass through the cell membrane. Exocytosis – membrane-enclosed secret...

Vasectomy

By: Administrator, Views: 9861

Vasectomy Procedure: (A) The spermatic cords are located as they ascend from the scrotum. (B) The vas deferens are severed. (C) A 1 cm section is removed. (D) The cut ends cannot reconnect thereby preventing the passage of sperm cells and providing surgical sterilization.

Generalized life cycles for plants and animals Animation

By: HWC, Views: 507

But the life cycles of plants and animals differ in their details. In animals, a multicelled diploid stage gives rise to single-celled haploid gametes, the eggs and sperm. These gametes combine at fertilization to form a diploid zygote, which grows and develops into a new multicelled animal...

Junction Types - Tight and Adherens Junctions

By: HWC, Views: 7000

Many tissues contain in tercellular junctions between cells. 1. Tight junction 2. Adherens junction 3. Desmosome 4. Hemidesrnosome 5. Gap junction 1. Tight junction • Web-like strips of proteins fuse together adjacent plasma membranes. • Tight junctions prevent the transport...