Some species of present day protists contain living organisms within their cytoplasm. paramecium bursaria are hosts for zoochlorellae, photosynthetic protists, that live within the cytoplasm of the paramecium. the relationship appears to be symbiotic; the zoochlorellae gain protection and possibly some essential nutrients from the host cytoplasm and the paramecium host has an available food source when its usual food source is depleted. this symbiotic relationship provides support for the theory of endosymbiosis, which states that a) animal-like cells evolved from ancestors that were photosynthetic. b) mitochondria and chloroplasts evolved from small prokaryotes living within larger cells. c) photosynthetic organisms, like today's land plants, evolved from photosynthetic bacteria. d) heterotrophic organisms could not have evolved before the evolution of photosynthetic organisms.

Answer : The correct answer is-

B) mitochondria and chloroplasts evolved from small prokaryotes living within larger cells.

Endosymbiotic theory is an evolutionary theory that describes the origin of mitochondria and chloroplast (cell organelles of eukaryotes) from the prokaryotes.

These two organelles share characteristics with bacteria as they both have circular DNA, capable of self replication, transcription, and translation.

It is beleived that prokaryotes used to live in symbiotic association with larger cells and later they developed into these organelles (particularly "alpha proteobacteria" developed into 'mitochondria' and "cyanobacteria" developed to '' 'chloroplast').

According to this information, option B) is the right answer for  theory of endosymbiosis.

correct answer is option a.

tropopause, stratopause and mesopause have all in common aspect that is point of maximum temperature in its layer of the atmosphere. all layers of atmosphere observe abrupt change in temperature. tropopause is the boundary between troposphere and stratosphere. stratopause is the boundary between stratosphere and mesosphere. mesopause is the boundary between mesosphere and thermosphere. these all boundaries are ranges between altitude of 0 to 80 km.

answer:   option a) glucagon was secreted by his pancreas before he ate the cookies because blood glucose was low. insulin was secreted after he ate the cookies because his blood glucose was high.

explanation: