Which of the following caused mortality rates to significantly decrease, starting in the 17th century? High number of youth in the population
Decrease in infectious diseases
Hygiene, sanitation, healthcare
Agriculture and transportat

Which statement best describes a keystone species? o a. it has littlelmenetic variation. it has an extremely high population. 0 b. 0 c. it remains unaffected by all environmental changes. od. it has a strong influence on the ecosystem. 0 e. it's the first species to populate a new ecosystem.

This is the amino acid cysteine. circle the amine group, put a box aroundthe carboxylic acid group and use a different colored pencil/pen to circle the sidechain (r group). h o | ||nh2— c- c-oh | ch2 | sh

Sally and sue were investigating the topic of friction in science. they used a small car and a ramp as seen in the picture to test what they were learning. they knew that they slipped easily on waxed floors but not on carpet, so they decided to change the material on the surface of the ramp to see what happened. they planned to use glass, carpet, aluminum foil, and sandpaper and run the car down the ramp over each surface. what would be the best research question to guide the girls' experiment? a) does the amount of surface area affect the friction on the moving car? b) will the car travel fastest on the glass surface? c) how does the angle of the ramp affect the speed of the car? d)do rougher surfaces tend to create more friction than smooth surfaces?