GCSE Inheritance, Variation and Evolution Flashcards
Give an overview of sexual reproduction
Involves two parents that produce male and female gametes that fuse during fertilisation. Meiosis is used to make these gametes with 1/2 the number of chromosomes. Fertilisation causes the haploids to fuse and form a diploid zygote. Offspring have genetic variation from different combinations of alleles.
Give an overview of asexual reproduction
Involves one parent producing a clone of themselves via mitosis with the same number of chromosomes as the original parents. Offspring have no genetic variation and are genetically identical.
Give examples of sexual reproduction
Multicellular animals, tomatoes, oranges
Give examples of asexual reproduction
Yeast, amoeba, daffodil bulbs, potato tubers
What are the advantages of sexual reproduction?
Produces genetic variation in offspring, variation provides species with increased long term survival, selective breeding can speed up natural selection
What are the advantages of asexual reproduction?
Only 1 parent needed, more time & energy efficient, often produced in favourable conditions, often well adapted to environment + can easily colonise area
What are the disadvantages of sexual reproduction?
Time consuming to find a mate, energy needed to produce gametes, fewer offspring produced more slowly
What are the disadvantages of asexual reproduction?
Results in lack of competition in ecosystem (extinction more likely), cannot produce multicellular animals, limits evolutionary potential.
Define mitosis
the division of the nucleus of the cell to produce 2 new daughter nuclei (and therefore 2 new cells) that are genetically identical to the parent cell.
When does meiosis occur?
In sex organs to produce gametes for sexual reproduction
What is the start code for mRNA?
AUG (met)
What are the end codes for mRNA?
UAA, UAG, UGA
What is DNA made up of
Alternating sugar-phosphate strands connected by complimentary bases (T&A, C&G)
What are genes?
Sections of chromosomes that code for proteins.
What are chromosomes?
Long strands of DNA divided into genes.
How many pairs of chromosomes do humans have?
23
Why are chromosomes found in pairs?
One chromosome comes from each haploid sex cell to fuse during fertilisation.
What is a mutation?
A change in the DNA base sequence.
What can the human genome project be used for?
Study of genes linked to disease, considers likelihood of developing genetic disease, finds treatment for hereditary disease, traces human migratory patterns
What are the disadvantages of the HGP?
Ethical concerns: prejudice against certain genomes.
Health insurance companies might charge people w certain genomes more than others
How many different amino acids are there in the body?
20
How does DNA coding for protein synthesis reach the ribosomes?
mRNA is created.
What is mRNA?
A tiny molecule of single-stranded DNA with exposed bases that can fit through the pores in the nuclear envelope. It has base U instead of base T.
Describe the process of transcription in protein synthesis.
The DNA is ‘unzipped’ by DNA polymerase. A single
How might two different species evolve? (speciation)
- Two ancestral populations are separated by a geographical barrier. (isolation mechanism - islands)
- There is already genetic variation within this separated population (beak size and shape)
- In different environments (food source), natural selection occurs and causes the best adapted species (best beak) to survive and reproduce.
- This causes the advantageous allele to be passed onto offspring in each individual population (develops into new species)
When does extinction happen?
When the last living member of a species dies and the species ceases to exist.
What is an endangered species?
A species that is at risk of going extinct.
What are the three types of extinction?
Direct, indirect and natural
What is direct extinction?
When humans destroy so many animals/plants that they cease to exist.
What is indirect extinction?
Humans affect a habitat so much that it causes population to fall.
What is natural extinction?
When a species declines in numbers gradually but steadily at the end of its evolutionary period (speciation)
How did dodos go extinct?
They were flightless and ground-nesting. Humans brought pigs and rats to the island and preyed on the dodo’s eggs. The dodo could not adapt to these new conditions, so less were born and went extinct in 1660.
What are the five kingdoms?
bateria, protist, fungus, animal, plant
