Answer:
Pollen grain lands on stigma
Explanation:
A) Pollen grain lands on stigma
- pollen tube grows down the style
- generative cell divides, forming two sperm
- two sperm are discharged to them female gametophyte
- sperm fuse with the egg and two polar nuclei
- zygote forms and divides into a terminal cell and a basal cell
- cells of embryo differentiate into three tissue types---- seed dries out and becomes dormant.
B)
- During pollination, a pollen grain is transferred from an anther to a stigma. Once the pollen grain lands on a suitable stigma, it germinates and forms a pollen tube, a structure that grows down through the style to the ovary.
- Once in the pollen tube, the generative cell from the pollen grain divides by mitosis, forming two sperm. The sperm travel down the pollen tube and are discharged into the female gametophyte. In a process called double fertilization, one sperm fertilizes the egg, forming the zygote; the other sperm fuses with two polar nuclei in the female gametophyte, forming a triploid (3n) nucleus. The zygote develops into the plant embryo, and the triploid nucleus divides and gives rise to the endosperm. Double fertilization prevents the waste of the plant's resources by ensuring that the nutrient-rich endosperm only develops if the egg is fertilized.
- After double fertilization, the ovule starts to develop into a seed containing the plant embryo. As the embryo develops, the three tissue systems are established, and the cotyledons (seed leaves) form. The seeds of many species dry out as they mature. These dry seeds lie dormant until suitable germination conditions occur.
Answer:
A rainbow is caused by sunlight and atmospheric conditions. light enters a water droplet, slowing down and bending as it goes from air to denser water. The light reflects off the inside of the droplet, seperating into its component wavelengths-or colors when light exits the droplet, it makes a rainbow
Answer:
At heart, all life on Earth uses a membrane that separates the organism from its environment. ... In this regard, water is essential simply because it's a liquid at Earth-like temperatures. Because it flows, water provides an efficient way to transfer substances from a cell to the cell's environment.
Answer:
C)
Explanation:
Meiosis creates sex cells (gametes) for sexual reproduction. And the resulting daughter cells have have the number of chromosomes as the parent cell.
Answer:
When carbon dioxide is released into the environment, typically due to human activities and respiration in animals, it gets trapped in the atmosphere. Carbon dioxide is just one greenhouse gas, but as all of the gases accumulate in the Earth, the temperature begins to rise globally. There are many implications to this, including the melting of glaciers, bleaching of corals, and increasing necessity for air conditioning systems and ventilation. When glaciers melt, they become a part of the ocean, meaning that as more glaciers begin to thaw out, the ocean will being to grow up and out. As sea levels rise, humans and animals are left with no choice but to being moving to higher points of elevation to avoid sinking. Another consequence of glacial melting is the loss of habitat for animales in many environments. Those living in glacial areas will begin to lose the snow and ice they are built to withstand. Those living near the sea or at low points of elevation will lose their habitats as it sinks deeper into the ocean. Another problem with global warming is coral bleaching. As the ocean warms up from the rising temperature, corals will being to overheat until they become ”blaeched’ whihc essentially means that they die. Lastly, global warming will create an increasing necessity for air conditioning systems and ventilators. People who do not have access to these things or cannot afford them can risk health complications. Global warming is a problem that cannot be ignore and the world needs to take more steps to plant trees and grasses that can photosynthesize the carbon dioxide into oxygen.
