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(B - GCSE) Biology > B5 > Flashcards

B5 Flashcards

(84 cards)

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1
Q

What is a phenotype

A

Characteristics observed in an organism

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2
Q

What is variation

A

Differences in a species

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3
Q

What is a genotype

A

The combination of alleles present in an organism

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4
Q

What are the two main causes of variation

A

Genetic variation - variation caused by an organisms genetic materials (passed down from parents)

Environmental variation - variation caused by the environment

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5
Q

Give an example of genetic an environmental variation - one for humans and one for plants

A

Genetic

Blood group
Colour of flower

Environmental

Language spoken
Size of leaf

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6
Q

What causes the majority of variation

A

Most variation isnt genetic alone (in humans this is very rare)
Most variation in a species is caused by both environmental and genetic variation

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7
Q

What two groups can variation be divided into

A

Discontinuous - characteristics that fall into distinct groups (e.g Blood group)

Continuous - characteristics that fall between a maximum and a minimum (e.g height)

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8
Q

What is asexual reproduction

A

Reproduction which only requires one parent
It results in clones

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9
Q

What is sexual reproduction

A

Reproduction requiring two parents
Results in variation

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10
Q

What are the advantages and disadvantages of asexual reproduction?

A

Advantages:
-If the parent is well adapted to the environment its offspring will be to
- only one parent is needed, reproduction is faster so more offspring can ve produced quickly

Disavantage:
- advers changes to the abiotic or biotic environment can destroy the species as all organisms will be effected

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11
Q

What are the advantages and disadvantages of sexual reproduction

A

Advantages:
-Variation if offspring leads to adaptation in a species, these adaptations will help cope with changes in environmental pressures

Disadvantage:
- reproduction is slower as it requires two parents

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12
Q

What is meiosis

A

Cell division that produces gametes

4 genetically different haploid cell

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13
Q

What stages make up meiosis

A

Meiosis 1 :
Prophase 1
Metaphase 1
Anaphase 1
Telophase 1
Cytokinesis

Meiosis 2 :
Prophase 2
Metaphase 2
Anaphase 2
Telophase 2
Cytokenisis

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14
Q

What happens in Meiosis 1, prophase 1

A

(Chromosones condense into their sister chromatid pairs)
Homologous chromosomes pair up to form a tetrad (total of four chromatids)

They exchange alleles in a process called crossing over
Nuclear membrane breaks down
Spindle fibers form

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15
Q

What are homologous chromosomes

A

A pair of chromosomes that share the same genes

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16
Q

What are alleles

A

Different variations of a gene due to different DNA bases

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17
Q

What happens in Meiosis 1, Metaphase 1

A

The pairs line up randomly on the cells equator
Line up in two rows (two sets in a pair)

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18
Q

What happens in Meiosis 1, Anaphase 1

A

The pairs of chromosomes are separated
(NOT THE SISTER CHROMATIDS)
and pulled to opposite sides of the cell

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19
Q

What happens in Meiosis 1, telophase 1

A

Spindle fibers break down
Chromosomes condense
Nuclei reforms
Cell pinches

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20
Q

What happens in Meiosis 1, cytokinesis

A

The cells divide into two genetically different diploid cells

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21
Q

What happens in Meiosis 2, Prophase 2

A

Both cells enter this phase at the same time and DNA has not been replicated

Spindle fibers form
Nucleus breaks down
Chromosomes condense

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22
Q

What happens in Meiosis 2, Metaphase 2

A

Chromosomes line up on the equator

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23
Q

What happens in Meiosis 2, anaphase 2

A

Sister chromatids are separated and the chromosomes are pulled to opposite polls

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24
Q

What happens in Meiosis 2, telophase 2

A

Spindle fibers break down
Nuclei reforms
Chromosomes decondense

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25
What happens in Meiosis 2, cytokenisis
The cells split amd we are left with 4 genetically varied haploid daughter cells
26
What are sister chromatids
Identical copies of a chromosome formed by DNA replication
27
What are the two types of alleles and how they are represented
Dominant (Capital letter) Recessive (lowercase letter) Use the same letter for Dominant and Recessive alleles
28
What does heterozygous mean (alleles)
One recessive and one dominant allele
29
What does homozygous mean (alleles)
The alleles are the same type Either homozygous dominant or homozygous recessive
30
What is a dominant allele
An allele (sequence of different DNA bases that codes for the same protein) where only one is required to be shown in the phenotype
31
What is a recessive allele
Two alleles ( sequence of different DNA bases that codes for the same protein) are needed to be expressed in the phenotype
32
How does genetic variation occur?
You share an allele with each parent the dominant one (if present will be observed) During miosis alleles cross over causing you to have a different sequence of genes
33
Complete this genetic cross for the offspring Male - Brown eyes Female - blue eyes The man is Homozygous recessive The female is homozygous dominant
Male. Female Pheno: brown. Blue Genotype: bb. BB Female B. B Male. b. bB. bB b. bB. bB bB = 100% = blue eyes The offspring will have blue eyes
34
What does it mean if someone is a carrier (genes)
They have a recessive gene that is not shown in the phenotype
35
How many genes in a Y chromosome
100
36
How many genes in an X chromosome
1000
37
What chromosomes do females have and which do males have
Female - XX Male XY
38
What is a gene
A sequence of DNA bases that codes for specific proteins
39
What is mutation
A change in the DNA base sequence
40
What are the main causes of mutation
Exposure to radiation. (X - rays, Gamma rays, UV rays). Carcinogens (cause cancer) (smoking or asbestos) Errors in DNA replication
41
What are point mutations
One base that changes
42
What are the main ways DNA mutates
Substitution - a DNA base is swapped (Emg A for G) Insertion - base are added Deletion - bases are removed
43
Why can mutations be harmful
A change in the DNA base sequence can cause different amino acids to be used in protein synthesis
44
How many amino acids are there
20 amino acids
45
Why can one amino acid be coded by multiple DNA base arrangements (triplets)
There are 64 possible triplet combinations (4 bases triplet is free bases 4^3) And only 20 amino acids So most amnio acids are coded by multiple triplets They are degenerate
46
What are silent mutations
When a mutation occurs but the amino acid coded is still the same
47
What is a genetic VARIENT
A different version of an allele caused by a change in DNA bases
48
What are examples of harmful mutations
Some can cause cancer Cause the production of abnormal proteins They can cause different shaped proteins to be made
49
How do mutations alter phenotype
Mutation can cause the production of irregular proteins It can cause metabolic issues as these proteins (like an enzyme) no longer work effectively This can cause conditions like phenylketonaria
50
What did gregor mendel discover
1886 Carried out an experiment on peas - observing characteristics from parent to offspring 1) characteristics were determined by hereditary units (genes) 2) Hereditary units are passed down from parents (1 unit from each) 3) Hereditary units are dominant or recessive
51
What did Friedrich Meischer discover
He discovered an acid in the nucleus of a cell. This is DNA (acid called nuclein)
52
What did oswald avery discover
He transferred DNA from one bacteria to another (giving it an ability to pass disease) The bacteria passed this trait to its offspring This showed genes are made of DNA 1944
53
What did Erwin Chargaff discover
He found all DNA contains an equal amount of adenine, thymine, cytosine and guanine 1950
54
What did Maurice Wilkins and Rosalind Franklin do
They imaged DNA crystals using an x ray 1952
55
What did James Watson and Francis Crick do
They published their description of DNA, describing it as a double helix 1953
56
What was the Human genome project
A project that lasted over 20 years of identifying and sequencing around 24,000 genes - the complete set in the human body (Ended 2003)
57
What does it mean if a codon is degenerate
It codes for multiple amino acids
58
What is natural selection
The survival and selection of advantageous alleles This happens to something called survival of the fittest
59
What is evolution
A change in the phenotype of a species overtime Natural selection drives evolution
60
Give an example of natural selection
Peppered Moths During the industrial revolution many trees were covered in soot. The light coloured moths could no longer camouflage and were eaten The darjer noths survived and were able to reproduce, passing on the dark coloured gene
61
What is a selection pressure
A change in the environment
62
What is a species
A group of organisms that are able to interbreed or reproduce to produce fertile offspring
63
How can the geography of areas create new species
As the same species live in different environments - so they have different selection pressures As a result of these the allele frequency passed down increases but is different in both areas Over many generations the organisms will adapt to best suit their environment If the animals come back together and cant produce fertile offspring they are a different species
64
What is the fossil record
The fossil record shows where the fossils were found. Older fossils are found deeper
65
How are organisms preserved
Animals encased in amber are preserved perfectly as there is no oxygen. So they cannot be decomposed. Fossils show an animals bone structure
66
How are fossils formed?
FOSSILS ARE NOT THE ACTUAL BONES OF ANIMALS After the skeleton is covered in sand, soil or clay it becomes mineralised over millions of years and the skeleton turns into rocks. (Mineralisation - minerals enter the bones and remove oxygen so its bot decomposed) The rocks shift in the Earth with the fossil trapped inside. Eventually the fossils emerge as the rocks move and erosion takes place
67
What other examples are there for evolution - other than the fossil record
Rapid change in a species - as bacteria replicate rapidly scientists observe its evolution, like how a characteristic with antibiotic resistance is passed down Extinction - Species that dont evolve or adapt will die out. 99% of all species are dead Molecular comparison - DNA and proteins of different animals can be compared
68
Who created the theory of Evolution
Charles Darwin
69
What book was the theory of evolution first published in
On the Origins of species
70
How did Darwin come up with his theory (Natural selection)
While on the Galapagos islands he noticed that on each island there was a different species of finch. The finches were closely related but had different shaped beaks or claws. Darwin realised that their beaks were shaped differently due to the food available on each island He said that the birds with the wrong beaks would die and overtime the birds least suited would be able to reproduce, passing down these advantageous characteristics. Eventually all the finches would share the characteristic
71
What is classification
Sorting organisms into groups based on their observable characteristics
72
What is taxonomy
Naming and defining an organism based on sharef characteristics
73
What are the 8 taxonomic levels
Domain Kingdom Phylum Class Order Family Genus Species
74
What are the domains
Bacteria, archae (sometimes just prokaryotes) Eukaryote
75
What are the 5 kingdoms
Prokaryotae Protoctista Plantae Animalia Fungi
76
What is Binomial Nomenclature
The process of naming Using the genus and species Homo sapiens Homo is the genus and Sapiens is the species
77
What is artificial classification
Clarifying organisms by appearance (including bone structure and behaviour)
78
What is a problem with using artificial classification
It's difficult to gain an accurate classification. Some species may have the same characteristics but ve conpletely different
79
What is natural classification
The classification of organisms based on evolutionary relations This used similarities in DNA base sequences to see how closely related to a species another is If the species are closely related they have shared a common ancestor more recently
80
What is the common ancestor all organisms evolved from
Luca - the Last universal common ancestor Was believed to be a unicellular aquatic organism
81
What is phylogeny
The study of evolutionary links
82
What do branches in a phylogenetic tree show
Where two branches meet is where the last common ancestor was
83
What is a phylogenetic tree
A tree showing different organisms and the links between them. This could be seen in any taxonomic level
84
Why is the fossil record incomplete
Fleshy bodied organisms are fully broken down Tectonic movements break up fossils

(B - GCSE) Biology (8 decks)

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