1. A seed leaf - cotyledon
2. A flowering plant with seeds that have two seed leaves - dicotyledon
3. A food storage tissue - endosperm
4. A flowering plant with seeds that have one seed leaf cotyledon - monocotyledon
Answer:
The stratum basale
Explanation:
The stratum basale contains basal keratinocytes, immune cells such as Langerhans cells and T cells, and melanocytes that provide the skin with pigmentation.Apr 12, 2019
Answer:
Hair is made of a tough protein called keratin. A hair follicle anchors each hair into the skin. The hair bulb forms the base of the hair follicle. ... Blood vessels nourish the cells in the hair bulb, and deliver hormones that modify hair growth and structure at different times of life, if that answers your question.
Explanation:
There are all sorts of ways to reconstruct the history of life on Earth. Pinning down when specific events occurred is often tricky, though. For this, biologists depend mainly on dating the rocks in which fossils are found, and by looking at the “molecular clocks” in the DNA of living organisms.
There are problems with each of these methods. The fossil record is like a movie with most of the frames cut out. Because it is so incomplete, it can be difficult to establish exactly when particular evolutionary changes happened.
Modern genetics allows scientists to measure how different species are from each other at a molecular level, and thus to estimate how much time has passed since a single lineage split into different species. Confounding factors rack up for species that are very distantly related, making the earlier dates more uncertain.
These difficulties mean that the dates in the timeline should be taken as approximate. As a general rule, they become more uncertain the further back along the geological timescale we look. Dates that are very uncertain are marked with a question mark.
