Name and explain two factors that affect population growth rates.

Logistic growth presupposes that the growth rate is dependant on population density and restricted by carrying capacity (limit to growth). Such growth is typically represented by an S-curve, whereby the growth rate declines as the population increases.

Exponential growth is math term meaning the larger the quantity gets, the faster it grows. So, if a population is growing exponentially, the larger the population, the faster the population grows.

Sigmoidal growth is characterized by initial sow growth, followed by rapid growth and eventually limited by saturation.


Population is obviously effected by the number of births, number of deaths, immigration, and emigration. If you're referring to population growth in lets say animals, such factors contributing to growth or decline would be the availability of food, number of predators, etc.

The worldwide human population is currently experiencing a population growth phase, and presently is increasing at an exponential rate. The death rate is decreasing, and the birth rate is increasing.

The competitive exclusion hypothesis states that two species with the same resource requirements cannot occupy the same niche; in other words, complete competitors cannot coexist.

The Allee effect is used to describe a population that has become so small that it will have difficulty surviving and reproducing. Density-dependent factors are related to the Allee effect.

1. I think you can divide them into intrinsic (fertility rate, normal life expectancy), and extrinsic (environmental, biotic or abiotc, like food availability) factors. Maybe someone else here can offer a better answer to this question.

2. Already answered

3. The human population is following an exponential growth, it is growing as if there are no limiting factors (of course other than the intrinsic ones). This is the case because overtime, whenever humanity faced a limiting factor, we overcame it with technology, and so in technologically advanced societies, at least so far, every possible limiting factor have been overcome (food availability, other resources, physical space (room to live)).

5. Lets say that in a particular ecosystem we have a top carnivore that is the wolf, a herbivore that is the rabbit. If wolves were to be removed from that population, then we would be removing a limiting factor for rabbits' growth, and so their population would increase greatly in size, and this population feeds on grass, which will no longer exist in enough amounts to sustain such a growing popuation of herbivores, so food becomes scarce, and rabbits start to die as well. If there was another population of herbivores competing over the same resource then their population would be affected as well (even if they weren't the prey of the removed carnivore). I'm not sure i gave the right answer, but everyone is welcome to add to it.

6. Can't help you on that one too.

Let's look at this from top-down. If the top carnivore is overhunted, for instance, the population directly beneath will increase as a direct result. They in turn will reduce the animals or species they eat, and this will result in a breakage of the food chain in which they are in. This is over simplified, but I hope you get the idea.

In any natural area, at a given time, there will be a community of plants, animals and microorganisms. As these change that area, the ecosystem becomes more adapted to a different range of organisms. So, over time, the species that make up the ecosystem change. That is succession. Take a meadow, for example. Over time, bushes will start to replace the wild flowers, then trees will start to grow, and eventually, given the right climate, the meadow will become a forest. Succession is most easily seen in disturbed sites - sites of forest fires, reclaimed gravel pits, etc.

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One other quick question i have is that Can u give me an example of each type of survivorship (Type I, Type II, Type III). I know what they are but can u just explain how each of the survivorship relates to population change. THNX

Hey Livestrong136,

Check this diagram out



OR...

https://biology-forums.com/index.php?action=gallery;sa=view;id=1378

Here's a clearcut explanation:

Survivorship curves generally fall into one of three patterns (the figure I linked to the gallery). In a type I curve, the rate of loss for juveniles is relatively low, and most individuals are lost later in life, as they become older and more prone to sickness and predators (see the Featured Investigation that follows). Organisms that exhibit type I survivorship have relatively few offspring but invest much time and resources in raising their young. Many large mammals, including humans, exhibit type I curves. At the other end of the scale is a type III curve, in which the rate of loss for juveniles is relatively high, and the survivorship curve flattens out for those organisms that have survived early death. Many fish and marine invertebrates fit this pattern. Most of the juveniles die or are eaten, but a few reach a favourable habitat and thrive. For example, once they find a suitable rock face on which to attach themselves, barnacles grow and survive very well. Many insects and plants also fit the type III survivorship curve, because they lay many eggs or release hundreds of seeds, respectively. Type II curves represent a middle ground, with fairly uniform death rates over time. Species with type II survivorship curves include many birds, small mammals, reptiles, and some annual plants. The beaver population most closely resembles this survivorship curve. Keep in mind, however, that these are generalized curves and that few populations fit them exactly.

Thnx alot that cleared everything