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(B - GCSE) Biology > B5 > Flashcards

B5 Flashcards

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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
Q

What happens in Meiosis 2, cytokenisis

A

The cells split amd we are left with 4 genetically varied haploid daughter cells

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26
Q

What are sister chromatids

A

Identical copies of a chromosome formed by DNA replication

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27
Q

What are the two types of alleles and how they are represented

A

Dominant (Capital letter)
Recessive (lowercase letter)

Use the same letter for Dominant and Recessive alleles

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28
Q

What does heterozygous mean (alleles)

A

One recessive and one dominant allele

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29
Q

What does homozygous mean (alleles)

A

The alleles are the same type
Either homozygous dominant or homozygous recessive

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30
Q

What is a dominant allele

A

An allele (sequence of different DNA bases that codes for the same protein) where only one is required to be shown in the phenotype

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31
Q

What is a recessive allele

A

Two alleles ( sequence of different DNA bases that codes for the same protein) are needed to be expressed in the phenotype

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32
Q

How does genetic variation occur?

A

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

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33
Q

Complete this genetic cross for the offspring

Male - Brown eyes
Female - blue eyes
The man is Homozygous recessive
The female is homozygous dominant

A

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

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34
Q

What does it mean if someone is a carrier (genes)

A

They have a recessive gene that is not shown in the phenotype

35
Q

How many genes in a Y chromosome

A

100

36
Q

How many genes in an X chromosome

A

1000

37
Q

What chromosomes do females have and which do males have

A

Female - XX

Male XY

38
Q

What is a gene

A

A sequence of DNA bases that codes for specific proteins

39
Q

What is mutation

A

A change in the DNA base sequence

40
Q

What are the main causes of mutation

A

Exposure to radiation. (X - rays, Gamma rays, UV rays).

Carcinogens (cause cancer) (smoking or asbestos)

Errors in DNA replication

41
Q

What are point mutations

A

One base that changes

42
Q

What are the main ways DNA mutates

A

Substitution - a DNA base is swapped (Emg A for G)

Insertion - base are added

Deletion - bases are removed

43
Q

Why can mutations be harmful

A

A change in the DNA base sequence can cause different amino acids to be used in protein synthesis

44
Q

How many amino acids are there

A

20 amino acids

45
Q

Why can one amino acid be coded by multiple DNA base arrangements (triplets)

A

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
Q

What are silent mutations

A

When a mutation occurs but the amino acid coded is still the same

47
Q

What is a genetic VARIENT

A

A different version of an allele caused by a change in DNA bases

48
Q

What are examples of harmful mutations

A

Some can cause cancer
Cause the production of abnormal proteins
They can cause different shaped proteins to be made

49
Q

How do mutations alter phenotype

A

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
Q

What did gregor mendel discover

A

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
Q

What did Friedrich Meischer discover

A

He discovered an acid in the nucleus of a cell.
This is DNA (acid called nuclein)

52
Q

What did oswald avery discover

A

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
Q

What did Erwin Chargaff discover

A

He found all DNA contains an equal amount of adenine, thymine, cytosine and guanine

1950

54
Q

What did Maurice Wilkins and Rosalind Franklin do

A

They imaged DNA crystals using an x ray

1952

55
Q

What did James Watson and Francis Crick do

A

They published their description of DNA, describing it as a double helix

1953

56
Q

What was the Human genome project

A

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
Q

What does it mean if a codon is degenerate

A

It codes for multiple amino acids

58
Q

What is natural selection

A

The survival and selection of advantageous alleles

This happens to something called survival of the fittest

59
Q

What is evolution

A

A change in the phenotype of a species overtime

Natural selection drives evolution

60
Q

Give an example of natural selection

A

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
Q

What is a selection pressure

A

A change in the environment

62
Q

What is a species

A

A group of organisms that are able to interbreed or reproduce to produce fertile offspring

63
Q

How can the geography of areas create new species

A

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
Q

What is the fossil record

A

The fossil record shows where the fossils were found.

Older fossils are found deeper

65
Q

How are organisms preserved

A

Animals encased in amber are preserved perfectly as there is no oxygen. So they cannot be decomposed.

Fossils show an animals bone structure

66
Q

How are fossils formed?

A

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
Q

What other examples are there for evolution - other than the fossil record

A

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
Q

Who created the theory of Evolution

A

Charles Darwin

69
Q

What book was the theory of evolution first published in

A

On the Origins of species

70
Q

How did Darwin come up with his theory
(Natural selection)

A

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
Q

What is classification

A

Sorting organisms into groups based on their observable characteristics

72
Q

What is taxonomy

A

Naming and defining an organism based on sharef characteristics

73
Q

What are the 8 taxonomic levels

A

Domain
Kingdom
Phylum
Class
Order
Family
Genus
Species

74
Q

What are the domains

A

Bacteria, archae (sometimes just prokaryotes)
Eukaryote

75
Q

What are the 5 kingdoms

A

Prokaryotae
Protoctista
Plantae
Animalia
Fungi

76
Q

What is Binomial Nomenclature

A

The process of naming
Using the genus and species

Homo sapiens

Homo is the genus and Sapiens is the species

77
Q

What is artificial classification

A

Clarifying organisms by appearance (including bone structure and behaviour)

78
Q

What is a problem with using artificial classification

A

It’s difficult to gain an accurate classification. Some species may have the same characteristics but ve conpletely different

79
Q

What is natural classification

A

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
Q

What is the common ancestor all organisms evolved from

A

Luca - the Last universal common ancestor

Was believed to be a unicellular aquatic organism

81
Q

What is phylogeny

A

The study of evolutionary links

82
Q

What do branches in a phylogenetic tree show

A

Where two branches meet is where the last common ancestor was

83
Q

What is a phylogenetic tree

A

A tree showing different organisms and the links between them.

This could be seen in any taxonomic level

84
Q

Why is the fossil record incomplete

A

Fleshy bodied organisms are fully broken down

Tectonic movements break up fossils

(B - GCSE) Biology (8 decks)

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