First, there is a need to understand what the carrying capacity is as it relates to the environment:
- Carrying capacity refers to the maximum number of individuals of a particular species that and environment can support based on the resources it has. 
- The population of a species in an environment grows and oscillates around the carrying capacity of the environment.
Now let us look at the graph. The population size grew from 0 and then leveled off at 2,000 with time. The leveling-off also happened without any oscillation, meaning that the maximum population size the environment can support is 2,000. 
Hence, the portion on the graph that indicates the carrying capacity would be the plot where the population size is 2,000 and the time being between 12 and 18. This has been circled and labeled as 'K' in the attached image.
More about carrying capacity can be found here: brainly.com/question/20270121
 
        
             
        
        
        
Answer:
For question 20. I believe the answer is C. There would be more iguanas with webbed feet.
Explanation:
It states the iguanas have adapted to different habitats on the island. The iguanas that have webbed feet will be better at getting food in water, but slower on land. So if the land starts to disappear and turns into more water, the iguanas with webbed feet will have a higher chance of survival. Meaning the iguanas with out webbed feet will die out as a population.
 
        
             
        
        
        
Answer:
When you breathe in, the diaphragm moves downward toward the abdomen, and the rib muscles pull the ribs upward and outward. This makes the chest cavity bigger and pulls air through the nose or mouth into the lungs.
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Answer:
D. If all of the offspring are short-tailed, the unknown individual is the homozygous dominant genotype.
Explanation:
The short tail phenotype is completely dominant over the long tail phenotype. When a short tailed salamander with unknown genotype is crossed with a homozygous recessive long tailed salamander, the cross is called testcross. Lets assume that the allele "S" gives "short tail" phenotype while the allele "s" gives "long tail" phenotype. 
If the "short tailed salamander" with unknown genotype is homozygous dominant (SS), the process of the testcross will express only dominant trait (cross 1). On the other hand, if the "short tailed salamander" with unknown genotype is heterozygous dominant (Ss), segregation of alleles during gamete formation would form two types of gametes (cross 2). The 50% progeny would express the "long tail" phenotype while rest 50% will express the "short tail" phenotype.