Genetics, populations, evolution and ecosystems Flashcards Preview

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Flashcards in Genetics, populations, evolution and ecosystems Deck (28):

What is ecology?

The study of the inter-relationships between organisms and their environment.


What's the difference between biotic and abiotic factors?(give examples)

Biotic factors are factors that refer to living things e.g. Competition, predation
Abiotic factors are factors that refer to non-living thing e.g. Temperature, rainfall or light intensity.


Define an ecosystem.

A dynamic system made up of a community and all the abiotic factors of its environment.


Define a population.

A group of individuals of one species that occupy the same habitat at the same time and are potentially able to interbreed.


What is a carrying capacity?

The certain size of a population which an ecosystem can support(dependant on biotic and abiotic factors).


Define a community.

All the populations of different species living and interacting in a particular place at the same time.


Define a habitat.

A place where an organism normally lives and is characterised by physical conditions and other types of organisms present.


What are microhabitats?

Smaller units within each habitat that each have their own microclimate.


What is a niche?(3)

A niche describes where an organism lives and what it does there
It includes all the biotic and abiotic contains to which an organism is adapted in order to survive, reproduce and maintain a viable population
No two species occupy exactly the same niche- this is known as the competitive exclusion principle.


What are the 4 main abiotic factors that effect population growth?(4)

-water and humidity.


How does temperature effect population size?(2)

Each species has a specific optimum temperature for functioning below and above this there is a reduced carrying capacity as fewer organisms can survive (e.g. Below optimum slower metabolism and above enzymes denature)-in plants a cold blooded animals
In warm-blooded animals despite being able to regulate body temperature, the further away from optimum the external temperature is the more energy is expended trying to maintain temperature and hence reproductive and growth rates slow hence a reduction in carrying capacity.


How does light effect population size?(2)

Basic necessity for light as provides more energy for photosynthesis meaning bigger plants and a greater carrying capacity similarly for animals who feed on plants the carrying capacity is also potentially larger.


How does pH effect population size?(1)

This effects enzyme action, each enzyme has an optimum pH-the more appropriate the pH the the larger the pop and vice versa.


How does water and humidity effect population size?

With a lack of water only species adapted to dry conditions can survive and small pop'
Humidity effects transpiration rates in plants and evaporation of water from animals, again those populations adapted to tolerate low humidity will be larger than those who are not.


Population growth=

(Births + immigration) - (deaths + emigration)


Percentage population growth rate (in a given period)=

Population change during the period/ population at the start of the period x100


What's the difference between inter and intraspecific competition?

Interspecific comptetition is when different species compete for resources whereas intraspecific competition occurs when individuals of the same species compete with one another for resources.


What is the competitive exclusion principle?(3)

when there is interspecific competition one species will normally have a competitive advantage over the other
this population of this species will increase whilst the other will decrease
if this continues then the less advantageous species will diminish completely.


How is it difficult to prove competition is the reason for variations in population.(4)

-there are many other factors that effect pop size
-a causal link has to be formed to show comp is the cause of any observed correlation
-time lag between competition and population change
-data on natural population sizes are hard to obtain and not always reliable.


When does predation occur?

When one organism (prey) is consumed by another (predator).


Evidence collected in predator and prey populations in a laboratory aren't representative of their interactions in the wild.
True or False?

True-the area over which the population of prey can travel is greater and the environment is much more diverse therefore there is a slim chance that all prey will be caught as there are a lot more places of refuge, in a laboratory there is less of this therefore the predators usually destroy all prey.


Explain how the relationship between predator and prey effect their populations.(5)

-Predators eat their prey thereby reducing the prey pop'
-With fewer prey available the predators are in greater competition
-this leads to a decrease in predator pop as fewer can obtain enough prey to survive or reproduce
-with fewer predators less prey are eaten so can survive and reproduce leading to an increase in their pop
-with more prey pop the predator pop in turn increases and this cycle will start again.


What does the hardy-Weinberg principle predict?(3)

The frequency proportion of alleles
Will stay constant from one generation to the next
Providing there are no mutations etc.


What is the evidence that non-agouti and blotched are alleles of different genes?

Add up to more than one.


What is the hardy-Weinberg principle?



What causes speciation?(4)

Reproductive isolation (sympatric speciation)
Geographical isolation (allopatric speciation)
Differences in gene pools


Describe how geographical barriers may lead to speciation.(5)

-geographical barriers prevent migration
-mutations occur in gene pools of one or each pop'
-advantageous in different pops' due to different selection pressures
-this leads to a change in allele frequencies in the pops' with them becoming increasingly different
-until unable to interbreed even if the barrier were to be removed as too genetically different.


Suggest how population size effects allopatric speciation.(4)

-small pop size=lower genetic diversity and not equal chance of passing on alleles but genetic information passed a lot quicker therefore a change in the allele frequency would be quicker hence speciation is more probable
-alternative for large pop'.