1.some of the fossils that have been found from before the cambrian explosion are embryos this suggests that the organisms these fossils belong to
a. have bilateral symmetry
b. reproduce asexually
c. exhibit cephalization
d. reproduce sexually
2. most of the body features found in invertebrates evolved during which of the following periods?
a. jurassic
b. cambrian
c. cretaceous
d. permian
3. a marine biologist exploring a deep sea trench locates a new species of soft bodied creatures with an unfamiliar shape. he is able to determine that the creature is a mollusk because it has
a. bilateral symmetry
b. body segmentation
c. an internal shell
d. am internal skeleton

1. D. reproduce sexually

2. B. Cambrian

3. A. bilateral symmetry

Explanation:

The formation of an embryo (zygote) is a characteristic of sexual reproduction since it occurs as a result of the union of a female gamete with a male gamete.The Cambrian is the period in which most groups of animals appear in the fossil record. The animals that characterize the Cambrian fauna are basically groups of invertebrates such as annelids, arthropods, porifers and echinoderms.Of the described options, the only characteristic of mollusks is bilateral symmetry, since they are not segmented and are soft-bodied animals, ie, they don't have internal skeletons or shells.

1. true.2. true.3. true.4. false.5. true.the concept of darwin's theory of evolution involves the idea that there are limited resources in a given living environment and that the organisms which live within have variations in their genetic make up due to random mating. the ones with beneficial genetic variations can express certain traits which give them an upper hand in surviving and reproducing in the said environment compared to ones who may have a more disadvantageous variation in traits. over time, the organisms with an upper hand will survive and reproduce more frequently and pass on their beneficial genes while the others die. the result is evolution, where we observe (usually, but not always) eventually, phenotypic distinct changes.