Question

4. Below is a diagram showing the geographic distribution (in black) of the bald eagle (Haliaeetus leucocephalus) across North America a) Does the diagram to the right show their realized or fundamental niche? b) Describe the difference between the two niches. c) Bald eagles are territorial birds. Based on this, what type of small-scale distribution do they have? d) Is their small-scale distribution the same as their distribution observed at a large-scale? If not, what type of distribution is observed at a large-scale? e) Although all bald eagles are the same species there are distinct groups spread across the continent. What do we call these groups if individuals migrate between 2 or more geographically- separated populations? f) How might gene flow between geographically-separated populations be advantageous for the entire species (hint - think about what is maintained)? Bald eagle range in black

Answer 1

First of all, what is a niche?

Niche of a particular species refers to the ways in which they interact with their environment.

Fundamental niche is defined as the entire set of conditions under which a particular animal (refers to a population or species) can survive and reproduce itself. Realized niche is the set of conditions which is actually used by that animal, after interactions with other species (predation and especially competition) that has been taken into picture. The diagrammatic representation given below would explain this concept better.

Realized Niche Prey size Fundamental Niche Fitness (for individual) or population growth rate (for pops) is zero outside this line Temperature

Now coming to the diagram,

Consider comparing the natural resource map and population map with the diagram given above to understand the type of niche exhibited.

婚兀 Bald eagle range in black Population density Natural Resource

Before concluding, it is also important to understand the nature of Bald Eagles. Bald eagles are sensitive to human activities, therefore they will make their nests as far away from human disturbance as possible. But in the picture given covers even areas where population is dense in the east. Moreover, most of their diet is comprised by fish, but they may also often eat the carcasses of small mammals like rabbits, hares, squirrels, raccoon, and other such terrestrial prey. They tend to live near wetlands, large coasts, inland waters, or marshes, from which they source their fish-based diets but the area covers even the central tropical and temperate grasslands. So, we can conclude that it denotes the Fundamental Niche of the Bald Eagles.

Let us consider the two types of eagles:

African fish eagle Bald eagle

They might look similar but belong two different species. According to the most widely used species definition, the biological species concept, a species is a group of organisms that can potentially interbreed, or mate, with one another to produce viable, fertile offspring.

Gene flow is otherwise called as gene migration. Gene flow can take place between two populations of the same species through migration, and also between different species. In such cases, where the inbreeding members are biological species, then the gene flow is is mediated by reproduction and vertical gene transfer. In such cases, the offspring contains the gene which would be expressing the characteristics of both the parents.