Answer:
With millions of different kinds of organisms in the world, scientists must find order in all of this diversity. Scientists group living organisms into one or more of a few major categories as part discipline known as taxonomy. The bodies of organisms are organized into functional systems—cells are organized into tissues, and tissues are organized into organs. Body systems carry out critical functions, such as locomotion, reproduction, digestion, and circulation. All living things on Earth are composed of the same carbon-based, molecular building blocks.

If I am correct it is The Third Trimester
They are composed of actin, troponin, tropomyosin, and myosin
A Eukaryotic cell engulfing a bacterial cell.
You may want to know that the bacteria which used to photosynthesise , after they have been engulfed by an eukaryotic cell , they evolved into Chloroplasts .
However for the bacteria which used to respire , they have evolved into mitochondria.
Hope this helps :) Good Luck !
The mitochondria is the site of respiration and energy production.