It is widely believed that humans first arrived in the Americas around 13,000 to 15,000 years ago. Discoveries at archeological sites such as Mesa Verde in Chile and Meadowcroft, PA have long supported this view. At a dig in Southern California, possible traces of human activity from over 130,000 years ago have been discovered. Researchers at the site recovered the partial skeleton of a mastodon, an … Continue reading When did the Americas encounter the first human?
Cross section of oak wood, showing every reason that made an oak tall and strong. The large pores are vessels that are responsible for transporting (more accurately, pumping/pushing) water from the root system to the tip of the tree. The densely packed purple dots are stained lignin in the cells walls. During early wood development, once lignin is deposited in the cell wall, these cells … Continue reading Oak Wood Cross Section
Tangential section of wood of Chinese holly. This is how it looks like when you do a cut that’s perpendicular to the radius of the stem. The vertical lines are vessels transporting water from roots to leaves, while the circles are clustered ray cells that function to transport fluids and nutrients radially and laterally (perpendicular to the long axis) within a woody stem. Contributed by … Continue reading Holly Wood Tangential Section
Microscope image of the epidermis of a spiderwort leaf with well-organized stomata in high density. Stomata (singular stoma) are like little mouths on the leaf surface, specialized in gas-exchange – CO2 enters a plant through them. The opening and closure of stomata are tightly controlled, because when stomata are open, water is escaping from the plant too. Therefore, each plant needs to find a delicate … Continue reading Monocot Leaf Epidermis
Crown-of-thorns starfish (COTS) are decimating coral populations along the Great Barrier Reef. Scientists have sequenced COTS genomes in the hopes of turning their own biology against them. Researchers think they have found the peptides the COTS use to communicate with each other. These peptides are released into the water to help the starfish aggregate before spawning events. If true, it’s possible to use these peptides to build several mechanisms for controlling the COTS pests. Continue reading Using your own DNA against you: Bio-control of coral reef pest might be possible
Lower leaf epidermis of the stonecrop plants showing puzzle shaped epidermal cells with scattered stomata. Stomata (singular: stoma) are like little mouths on the leaf surface, specialized in gas-exchange – CO2 enters a plant through them. The pairs of sausage-shaped cells, like the lips of these mouths, are “guard cells”, which guard the opening and closure of the stomata. In many flowering plants, the stomata … Continue reading Dicot Leaf Epidermis
Unlike animals, plants possess the ability to generate new tissues and organs throughout their entire lifespans due to the activity of stem cells located in specific sites termed meristems. During the reproductive phase, floral meristem (lower right dome-shaped structure) give rise to different floral organ primordia (the series of bulges), which will eventually grow into the sepals, petals, stamens, staminodia, and carpels of a beautiful … Continue reading The Birth of a Flower