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Population fragmentation causes inbreeding depression, which leads to a decrease in genetic variability in the species involved. [4] This decreases the fitness of the population for several reasons. First, inbreeding forces competition with relatives, which decreases the evolutionary fitness of the species. [ 4 ]
Habitat fragmentation is often a cause of species becoming threatened or endangered. [25] The existence of viable habitat is critical to the survival of any species, and in many cases, the fragmentation of any remaining habitat can lead to difficult decisions for conservation biologists.
A population cycle in zoology is a phenomenon where populations rise and fall over a predictable period of time. There are some species where population numbers have reasonably predictable patterns of change although the full reasons for population cycles is one of the major unsolved ecological problems.
The ontogenetic niche shift varies across species; in some it is hardly visible and gradual (for example a change in diet or in size in mammals and reptiles), while in others it is obvious and abrupt (the metamorphosis of insects, which often results in changing habitat, diet and other ecological conditions).
The size and population of weta are affected by predation. Rats introduced on the mainland began to prey on weta, reducing their population; weta shrank in response. On an island isolated from predation, such as Little Barrier Island, weta have a dense population and have grown to a massive size. Insular species of giant weta are the only ones ...
Most large marine animal species still exist, such that the size distribution of global species assemblages has changed little since the Pleistocene, but individuals of each species are smaller on average, and overfishing has caused reductions in genetic diversity. Most extinctions and population declines to date have been driven by human ...
See more on climate change: A University of New Hampshire researcher says the horses, originally approximately the size of a dog, "may have gone down to the size of a cat." That's not the only bad ...
European mink (Mustela lutreola) is one of the most endangered mammal species, as its population drastically falls. Threats like habitat loss/fragmentation, overhunting, and the spread of the invasive American Mink (Neovison vison) have reduced their numbers over the years. Only around 3% of its former range is still occupied with around 5000 ...