1) What is intrinsic growth rate and relationship to births and deaths, what doe
ID: 178182 • Letter: 1
Question
1) What is intrinsic growth rate and relationship to births and deaths, what does it mean when r is positive, negative, or zero. Can you calculate it?
2) What's the Difference between logistic and exponential growth—type of organisms, speed and how related to carrying capacity?
3)How is natural selection, phenotype and genes involved?
4) Gene pool vs. geneotype vs. phenotype? whats Darwin’s role and finches? How are non-native plants introduced?
5) Biomes are defined by ____ and ____ as well as types of plants and animals ?
6) What are the Advantages of fires in our biome?
7) Which slopes in Northern hemisphere receive the most sun? and therefore this is where ___ plants are found? How is this different for tropics and southern hemisphere?
8) What is meant by native or indigenous compared to non-native?
9) What type of winters and summers due we have due to ___ ocean currents?
10) How are non-native plants introduced?
Explanation / Answer
A positive r – means the population is growing
A negative r – means the population is decreasing
Zero value of r indicates no change in population.
We can calculate it as
dN/dt = rN
where dN/dt = change in population over time t
r = intrinsic growth rate
N = population size
We can also say r = birth rate – death rate
2 ) Exponential growth can be defined as continuous increase (growth) in population in an environment with unlimited resource supply. It is a density independent growth. It follows a geometric or exponential growth curve.
Equation : dN/dt = rN
where dN/dt = change in population over time t
r = intrinsic growth rate
N = population size
Or Nt = N0ert
Where Nt = population size at time ‘t’ ; N0 = initial population size, r = intrinsic rate of increase and t = time.
Examples of species include – bacteria, diatoms, rodents
Environmental instability controls or reduces the population size before it reaches the carrying capacity.
Logistic growth can be defined as continuous increase (growth) in population in an environment with limited resource supply. It is a density dependent growth. Logistic growth follows a sigmoidal growth curve.
dN/dt = rN [ K- N/K]
where dN/dt = change in population over time t
r = intrinsic growth rate
N = population size
K = carrying capacity
Examples of the species include elephants, humans and whales.
Population is always near or approaching the carrying capacity due to density dependent factors.
3)Natural selection plays an important role in evolution. Over a period of successive generations, a change in genotype and phenotype is observed. phenotype is the expression of genes. Phenotype are a combination of genes and environmental influences. Individuals that exhibit phenotypes with provide fitness or advantage for survival and reproduction in the given natural environment are selected by nature. Thus genes that direct these phenotypes are selected and carried forward.
4) Gene pool is the total collection of all the genes; summation of total genetic information for a particular species. Genotype is the set of genes (specific alleles) that an individual possesses. It is the particular set of alleles for a specific gene present in the organism. Phenotype is the set of characteristics visible/expressed in an individual resulting from a combination of genetic makeup and environment.
Natural selection theory was given by Charles Darwin. The finches present on Galapagos Island are identical in all the ways except for their beak pattern. The beaks were adapted according to the food that they ate and occupied various niches present on the island. They have been isolated on the island for a long period. The gradation and diversity in beaks in the intimately related birds solidified the theory of natural selection.
Non-native plants are those species that have not been a part of the native range in the given area and have been introduced deliberately or accidentally by humans, birds or animals.
Non-native species may be intentionally transported to new locations and released into the wild or they species may escape from captive accidentally into new regions. Unintentional introductions may also occur when species are transported by human vectors.
Introduction may have positive or negative effect on the ecosystem.
For example, citrus originated in tropical to subtropical Southeast Asia and India and were introduced in Florida and have been proved to be beneficial. Apple snail was introduced in Southeast Asia for use as a protein source. Fast spreading plants such as garlic and mustard have been introduced to check soil erosion. Examples of unintentional introduction include spread of three common rat species – black, Norway and Polynesian via ships.
5) Biomes are defined by temperature and precipitation as well as types of plants and animals. Both biotic and abiotic factors such as plants and animals, rain, soil, geology and vegetation affect the biomes.
6) Fire has an integral role in maintaining the ecosystem. Certain plat species rely upon fire for growth and succession. Fires make the environments more hospitable for certain species. Wildlife fire prepares the soil for seeding, making a higher nutrient (in the form of ashes) availability for uptake and killing invasive plant species which compete with the native species. To elaborate further, fire also helps in controlling insect pests by killing old/diseased plants. It also helps in promoting biodiversity and healthy ecosystems. After the fire, seeds already present in the soil (native) grow quickly followed by other successional plants. Different plants, animals and microorganisms specializing in different niches cohabitate the area creating a new ecosystem.
7) In Northern hemisphere, south facing slopes generally receive mor sunlight as compared to north facing side. Plants that can tolerate these hot and dry conditions include chaparral and California buckwheat. During winters, north facing slopes remain shaded due to lower angle of the sun and remain cooler. Therefore shade loving plants grow here. Near the equator, tropics, north and south slopes both receive equal amount of sunlight.
8) Native species are plants, animals or other organisms that have been historically occurred and evolved in the given ecosystem.
Non-native species are those that have been intentionally or accidentally introduced to the given environment by human activities.
9) Which ocean currents do you mean?
10) Already answered in 4. It’s a repeat question.
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