Orcas, or killer whales, are natural predators of sea otters. it has been observed that in regions where the sea otters are not present, sea urchins grow rapidly and destroy much of the natural kelp vegetation. which of these statements is correct in this context? a) kelp is the keystone species because their survival is key to the survival of the entire ecosystem. b) sea otters cannot be considered the keystone species because they are not the top predators in the ecosystem. c) sea urchins are the keystone species because they multiply rapidly in the absence of their natural predators. d) sea otters are a keystone species as they prevent a herbivorous species from completely destroying a plant species.

The terrestrial planets are characterized by having a a.) silicate core b.) iron-rich silicate core c.) iron-rich metallic core d.) none of these

What problem would a person most likely have if her kidney did not work correctly?

You will create a molecular clock model for an arthropod gene. follow these guidelines to make your model: . your timeline will span from 90 million years ago to the present. the common ancestor in your model is an arthropod that lived 90 million years ago. the gene that you'll track codes for a protein in the species venom . the dna sequence youll track contains 10 nitrogen bases. you can choose the order of the bases and where the mutations occur. this gene mutates at a rate of approximately 0.76 base pairs every 17.1 million years. to build your model,/ calculate the estimated time period it takes for 1 base pair to mutate. the first time period will only show the common ancestor. at the beginning of the second time period, three lineages will diverge from the common ancestor, each with a different mutation in their gene sequences. the first and third descendant species will survive for the rest of the timeline. the second descendant species was extinct 50 million years ago. calculate how long it will take for one full base pair mutation to occur. explain your reasoning by constructing a mathematical equation