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Videos search results: "evolution"
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Post-copulatory sexual selection and sexual c... 
Male pregnancy in seahorses, pipefishes and sea dragons (family Syngnathidae) represents a striking reproductive adaptation that has shaped the evolution of behaviour and morphology in this group of fishes1. In many syngnathid species, males brood their offspring in a specialized pouch, which presumably evolved to facilitate male parental care5, 6. However, an unexplored possibility is that brood pouch evolution was partly shaped by parent–offspring or sexual conflict, processes that would result in trade-offs between current and future pregnancies. Here we report a controlled breeding experiment using the sexually dimorphic Gulf pipefish, Syngnathus scovelli, to test for post-copulatory sexual selection within broods and for trade-offs between successive male pregnancies as functions of female attractiveness. Offspring survivorship within a pregnancy was affected by the size of a male’s mate, the number of eggs transferred and the male’s sexual responsiveness. Significantly, we also found that embryo survivorship in a current pregnancy was negatively related to survivorship in the prior pregnancy, clearly demonstrating fitness trade-offs between broods. Overall, our data indicate that post-copulatory sexual selection and sexual c...
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Added By - autocrawler
Subject - Biology
Document Type - Journal Paper Discussion
Video Duration - moderate


adorable extremophiles 
Hank explains why NASA and the European Space Agency are in love with tardigrades and how these extremophiles are helping us study the panspermia hypothesis.
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Added By - samriddha
Subject - Biology
Document Type - Documentary
Video Duration - moderate


Nanotechnology - Age of Convergence 
We are approaching an evolutionary event horizon, where the organic and the synthetic, the virtual and the "real", are merging together into an operational ecology, an existence morphology for which there is no precendent in the history of which we are currently aware, catalyzed by nanotechnology. www.historianofthefuture.com
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Added By - 123456
Subject - Nanoscience and Nanotechnology
Document Type -
Video Duration - 00:04:33


Whales originated from aquatic artiodactyls i... 

In this video, Hans Thewissen and Lisa Cooper from the Northeastern Ohio Universities College of Medicine discuss their paper entitled "Whales originated from aquatic artiodactyls in the Eocene epoch of India", published in the Nature (Vol 450 Issue 7173 20 December 2007). Their co-authors include Mark Clementz, Sunil Bajpai and B.N.Tiwari.

Although the first ten million years of whale evolution are documented by a remarkable series of fossil skeletons, the link to the ancestor of cetaceans has been missing. It was known that whales are related to even-toed ungulates (artiodactyls), but until now no artiodactyls were mo...

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Added By - autocrawler
Subject - Biology
Document Type - Journal Paper Discussion
Video Duration - moderate


Blood: Path of a Red Blood Cell 

Red blood cells are the most common type of blood cell and the vertebrate body's principal means of delivering oxygen from the lungs or gills to body tissues via the blood.

Human red blood cellsRed blood cells are also known as RBCs, haematids or erythrocytes (from Greek erythros for "red" and kytos for "hollow", with cyte nowadays translated as "cell"). RBCs should more properly be referred to as "corpuscles" rather than "cells", as a cells contains a nucleus while mature RBCs in mammals do not.

A schistocyte is a red blood cell undergoing fragmentation, or a fragmented part of a red blood cell.

Erythrocytes consist mainly of hemoglobin, a complex molecule containing heme groups whose iron atoms temporarily link to oxygen molecules in the lungs or gills and release them throughout the body. Oxygen can easily diffuse through the red blood cell's cell membrane. Hemoglobin also carries some of the waste product carbon dioxide back from the tissues. (In humans, less than 2% of the total oxygen, and most of the carbon dioxide, is held in solution in the blood plasma). A related compound, myoglobin, acts to store oxygen in muscle...

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Added By - 123456
Subject - Biology
Document Type - Documentary
Video Duration - 00:00:02


Intelligent Design? Blood Vessels Help Tumors... 

Angiogenesis is a physiological process involving the growth of new blood vessels from pre-existing vessels. Though there has been some debate over this, vasculogenesis is the term used for spontaneous blood-vessel formation, and intussusception is the term for new blood vessel formation by splitting off existing ones.Angiogenesis is a normal process in growth and development, as well as in wound healing. However, this is also a fundamental step in the transition of tumors from a dormant state to a malignant state.

Intelligent Design? A scientist begins by asking a question that can be answered by gathering evidence. Questions arise in all sorts of ways: for example, from observations,...

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Added By - quantum
Subject - Medical Sciences
Document Type - Demonstration
Video Duration - 00:05:07


The Miracle in Human Brain 

How your brain works, amazing connections between billions of neuron cells.

In animals, the brain (enkephale) (Greek for "in the skull"), is the control center of the central nervous system, responsible for behavior. The brain is located in the head, protected by the skull and close to the primary sensory apparatus of vision, hearing, equilibrioception (balance), sense of taste, and olfaction (smell). While all  

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Added By - 123
Subject - Cognitive Science
Document Type - Discussion
Video Duration - 00:01:23

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