B6 Flashcards
Where is DNA found?
In the nucleus of a cell, in long structures - chromosomes
What’s a gene?
A small section of DNA that’s responsible for a characteristic
Function:
Code into amino acids
What’s an allele?
An alternative form of gene with multiple options.
Example:
Hair colour - blond, brown, black, ginger
Define homozygous
Two of the same alleles
Define heterozygous
Two different alleles
Define genotype
The genes and alleles which determine characteristics
Define phenotype
Characterisation expressed because of allele combination
What is a gamete?
Sex cells
Male - sperm
Female - egg
FORMED BY MEIOSIS
What is a dominant allele?
An allele that is always expressed, regardless of the second allele.
CAPITAL LETTER
What is a recessive allele?
An allele that is only expressed in the absence of a dominant allele.
SMALL LETTER
How many chromosomes are there in a human cell?
46
(diploid)
How many chromosomes in a gamete?
23
1 SEX CHROMOSOME
(haploid)
What is the difference in sexual and asexual reproduction?
Sexual reproduction:
Fusion of male and female gametes
Non-identical offspring
2 parents
Meiosis
Asexual reproduction:
Genetically identical offspring
1 parent
Mitosis
What is a genome?
An entire genetic material of an organism
Define variation
Difference in characteristics
What is variation caused by?
Mutation in DNA
Name the 3 types of variation
Genetic
Environmental
Both
Give 2 examples of genetic variation
Eye colour
Gender
Give 2 examples of environmental variation
Hair length
Ear piercing
Give 2 examples of genetic and environmental (both) variation
Height
Accent
Define evolution
Change in inherited characteristics of a population through natural selection
What is natural selection?
The process where organisms that are better suited to an environment are more likely to survive and reproduce
Give 2 reasons why species evolve
- More likely to survive
- Better at competing
- More likely to reproduce
How does evolution work (using alleles)?
Offspring will inherit advantageous allele
Why is the fossil record useful for the theory of evolution?
It shows how species have changed (evolved).
What are the 3 main ways fossils form?
- Gradual replacement by minerals
- Casts
- Preservation
Why is the fossil record incomplete?
The earliest fossils could’ve been destroyed by volcanoes/earthquakes
OR
The earliest organisms were soft bodied so there is no trace
Define classification
Sorting things into categories based on common features
Define extinction
Permanent loss of a whole species
Name 3 reasons for extinction
- Catastrophic event
Meteor - dinosaurs - Environmental change
Global warming - polar bears - New predators
Rats, pigs - dodo
Define selective breeding
Humans selecting animals/plants based on characterisitcs
Name the 3 stages of selective breeding
- Choose parents with desired characteristics
- Select the best offspring and breed to make the next generation
- Breed the offspring again until result is achieved
What did Linnaeus classify living things into?
Kingdom
Phylum
Class
Order
Family
Genus
Species
What changes have been made to the Linnaeus classification?
Domain ABOVE kingdom
(eukaryota, bacteria, archaea)
WHY? = due to development
Name the 5 classifications in kingdoms
Plants
Animals
Fungi
Bacteria
Protists
What is a biological name
Genus + species
Example:
Humans = homo sapiens
