Confidence votes 9.4K. Animal cells do not have cell walls, they only have cell membranes. The cell membrane mainly consists of a phospholipid bilayer, and also contains embedded proteins and cholesterol. Plant cell walls are mainly made of cellulose, bacterial cell walls are mainly made of peptidoglycan.
In the Northern Hemisphere, the official summer season begins with the June solstice, which takes place on June 20th, 21st or 22nd each year, and ends with the September equinox, which takes place on September 22nd or 23rd each year; the exact duration of summer depends on when the solstice and equinox will take place and can range from 92 to 95 ...
It's just what people say. The first day of winter you'll hear it's the shortest day of the year and for summer it's the opposite. It sounds silly, but it's a better reflection of day. A day only has 24 hours, so today can't be any longer than tomorrow. The sun rises at 6:13 a.m. here on the summer solstice and sets at 9:08 p.m. That's 14 hours and 55 minutes of daylight to enjoy! After Monday, the sunrise will continue getting a little later and the sunset a little earlier. Eventually by the winter solstice, we'll have a measly nine hours and 25 minutes of daylight.