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G-5 Population Ecology

Page history last edited by Jay 13 years, 6 months ago


 

G.5.1 Distinguish between r-strategies and k-strategies.

           An r-strategy involves investing more resources into producing many offspring, having a short life span, early maturity, reproducing only once and having a small body size. As an example for r-strategy, fish and insects will lay hundreds of eggs at a time, and rats often have large litters and are always fertile.

           In the other hand k-strategy involve investing more resources into development and long term survival. This involves a longer life span and slow maturity, and is more likely to involve prenatal care, the production of few offspring, and reproducing more than once. As a example humans and large mammals often have one offspring and have tendency to raise their offspring with close care.

           There are organisms (like humans and insects) that display extreme r- or k- strategies, but most organisms have life histories that are intermediate on the continuum.

           Some organisms such as Drosophila switch strategies depending on environmental conditions.

 

G.5.2 Discuss the environmental conditions that favor either r-strategies or k-strategies.

           In a predictable environment, in order to maximize fitness, it pays to invest resources in long-term development and long life (K-strategy). In an unstable environment, it is better to produce as many offspring as quickly as possible (r-strategy). Of concern is that ecological disruption favors r-strategies such as pathogens and pest species.

           Unstable environment is environment such as Tundra. Rangifer tarandus which lives in Tundra is able to breed an offspring when they are one years old. Other dear families living in more stable environment should reach age of 2 to be able to breed offspring. This fast paced breeding occur only to dears in Tundra because fast rate of breed help them to produce more and more number of offspring which help them to increase number of offspring. Rangifer tarandus have bigger possibility to leave their offspring alive in harsh conditions.

 

 

Stable environment usually support k- strategy. Stable weather, climate, food supplies and other abetting features to organism shapes organism to adopt k-strategy as a result of focusing one offspring to be more competitive.  

 

 

 

 

G.5.3 Describe one technique used to estimate the population size of an animal species based on a capture-mark-release-recapture method.

           There are actually various mark-and-recapture methods exist. To understand fully about these methods we need the knowledge of Lincoln index (which involves one mark-release-recapture cycle) is required.

(X*Y)/Z

 

Where X= number of individuals initially caught, marked and released, Y= total number of individuals caught in the second sample, and Z=numbers of marked individuals in the second sample.

 Although stimulations can be carried out, it is much more valuable if this is accompanied by a real exercise on a population of animals. The limitation and difficulties of the method can be fully appreciated, and some notion of the importance of sample size can be explained.

 

 

 

 

G.5.4 Describe the methods used to estimate the size of commercial fish stocks.

           Estimation of the size of commercial fish stocks can be done by various methods. Gathering information from fishers is one method. There is actually scientist who collects information on fishing vessels. Scientist have tasks like: recording the number and kinds of fish that are thrown back, tagging and releasing some fish, developing questionnaires for fishers about their perception of catch, and reviewing the logbook which gives catch-per-unit-effort data.

   Also Scientist uses professional research vessels. The scientist sample fishes with nets which is called trawling, using sounds to monitor fish population by using echo sounder which reads information from a pulse that is sends into the water. The returning echo indicates the presence of the school fish. Scientists also calculate population’s age to estimate the future changes on population. Scientists attach coded wire tag detector to mark fish population’s future location.

 

 

 

 

G.5.5 Discuss international measures that would promote the conservation of fish

 

In 2006, an international team of researchers came to a conclusion that by 2048 there will be no more commercial fishing. Fish population is decreasing in rapid speed. As a solution to the crisis, there are some ways to conservation fish populations.

-Regulate bottom trawling of the ocean because bottom trawling eventually strips mining of the ocean floor by large fleet of commercial vessels.

-Rebuild depleted fish populations as quickly as possible. Pay attention to the concept of maximum sustainability field.

-          -eliminate wasteful and damaging fishes practice

           -Enact strong national fish quota programs according to the concept of MSY.

           - Establish a programmes to develop less damaging fishing gear.

           -Encourage relationships between Scientist and fishers.

           -Establish marine reserves and no-catch zones to improve biodiversity and increase the numbers of fish stocks in areas that are protected.  

 

 

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