Topic 7 - Genetics and Ecosystems Flashcards
What is monohybrid inheritance?
the two parents differ in one characteristic breed
eg. Gg and gg
F1 offspring
first generation of offspring
F2 offspring
second generation of offspring
What is dihybrid inheritance?
the two parents differ by two characteristics breed
What is the ratio when two dihybrid heterozygous breed?
9:3:3:1
What are Co dominant alleles?
They are both expressed in a heterozygote.
eg. sickle cell anaemia
Describe how epistasis can affect the phenotype of an organism.
- epistasis alters expression of one gene based on the presence of another gene.
- a dominant gene masks expression of a recessive gene.
Describe how variations in alleles are.
Either heterozygous or homozygous.
What does the Hardy-Weinberg principle predict?
The freq of alleles will remain constant, over generations providing there are no mutations.
What is a gene pool?
All the alleles in a population
Describe one way scientists can determine whether two organisms from different populations are from the same species.
-Breed together
- if offspring fertile then same species
Give two features of a climax community:
- populations remain stable
- abiotic factors constant over time
Describe and explain the process of succession:
- Pioneer species
- a species changed the conditions eg. making conditions less hostile.
- new species better competitor
- pioneer species decreases new species increases
Two conditions for mark - release - capture investigations to be valid:
- marking does not affect survival eg. predation
- no breeding in the population
Why do the species present change during succession?
- species change the environment conditions (less hostile)
- other species better competitors
Describe how you could estimate the size of a population of a particular plant species in an area.
- use a grid to divide area into sections
- use a random number generator
- count freq in these randomly generated quadrants
- use a large sample to calculate the mean number of plants per quadrant
What is meant by uniformly distributed?
organisms are equally spread
How do assumptions made in proportional sampling differ from those made in mark-release-recatpure?
in mark release recapture:
- no assumption that organisms uniformly distributed
- size of total area not required
Give one assumption that is made in both proportional sampling and mark-release-recapture:
- animals are all part of same population
In genetic crosses, the observed phenotypic ratios are often not the same as expected ratios. Why?
- small sample size
- fertilisation of gametes is random
- epistasis
- linked genes
Causes of genetic variation in organisms:
- mutations
- crossing over
- random fertilisation of gametes
- independent segregation of homologous chromosomes
What is meant by the term phenotype?
Expression of characteristic due to genetic constitution and environment.
