iGCSE Edexcel Biology > Reproduction > Flashcards

Reproduction Flashcards

(145 cards)

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1
Q

What is sexual reproduction

A

Offspring made by fusion of male and female gametes

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2
Q

Why does sexual reproduction cause variation

A

Genetic material from two parents makes offspring different

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3
Q

How many parents in sexual reproduction

A

Two parents

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4
Q

What cells are used in sexual reproduction

A

Gametes

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5
Q

How are gametes made

A

Meiosis halves chromosome number

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6
Q

What happens after fertilisation

A

Zygote divides by mitosis to form embryo

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7
Q

What is asexual reproduction

A

Offspring from one parent no gametes no fertilisation

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8
Q

Why are asexual offspring identical

A

No mixing of genetic info so clones

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9
Q

Why is asexual reproduction faster

A

One parent no gametes no fertilisation

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10
Q

Main disadvantage of asexual reproduction

A

No variation so vulnerable to disease or change

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11
Q

Example of asexual reproduction

A

Many plants reproduce this way

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12
Q

How many parents in asexual reproduction

A

One parent

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13
Q

What cell division occurs in asexual reproduction

A

Mitosis

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14
Q

What cell division occurs in sexual reproduction

A

Meiosis to make gametes then mitosis after fertilisation

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15
Q

Genetic similarity in asexual reproduction

A

Offspring identical to parent and each other

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16
Q

Genetic similarity in sexual reproduction

A

Offspring genetically different from parents and each other

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17
Q

What are gametes

A

Sex cells made by meiosis

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18
Q

Examples of gametes in animals

A

Sperm and egg

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19
Q

Examples of gametes in plants

A

Pollen nucleus and ovum

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20
Q

Chromosome number in gametes

A

Half of body cells 23 in humans

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21
Q

Adaptation of sperm

A

Tail for movement mitochondria for energy

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22
Q

Adaptation of egg

A

Energy stores in cytoplasm for embryo development

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23
Q

What is fertilisation

A

Fusion of male and female gametes to form zygote

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24
Q

What happens after fertilisation

A

Zygote divides by mitosis to form embryo

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25
Chromosome number in zygote
46 chromosomes 23 pairs
26
Source of chromosomes in zygote
Half from father half from mother
27
Where does fertilisation occur in humans
Oviduct 1-2 days after ovulation
28
How does fertilisation occur in plants
Pollen tube grows male nucleus fuses with ovum in ovary
29
How many chromosones do gametes contain?
23 in human (half compared to normal)
30
What is the process of fertilisation in humans?
Semen ejaculated into female's vagina near cervix Sperm travels through cervix into uterus (follows chemical trail) Fertilisation occurs in oviduct if a sperm meets an egg (typically 1-2 days after ovulation)
31
What is a haploid nucleus
Contains a single set of chromosomes, meaning it has half the number of chromosomes as a diploid nucleus
32
What is pollination
Transfer of pollen from male part to female part of flower
33
Where are male gametes in plants
Pollen
34
Where are female gametes in plants
ovules
35
Adaptation of insect-pollinated petals
Large bright to attract insects
36
Adaptation of insect-pollinated scent and nectar
Produced to attract insects
37
Adaptation of insect-pollinated anthers
Stiff filaments inside flower so insects brush pollen
38
Adaptation of insect-pollinated stigma
Sticky inside flower to catch pollen from insects
39
Adaptation of wind-pollinated petals
Small dull green or brown (colourful would be waste of energy)
40
Adaptation of wind-pollinated scent and nectar
Not produced waste of energy
41
Adaptation of wind-pollinated anthers
Long filaments outside flower to release pollen easily
42
Adaptation of wind-pollinated stigma
Feathery outside flower to catch airborne pollen
43
How do insects transfer pollen
Brush anthers then stigma when visiting flowers
44
How does wind transfer pollen
Pollen blown from exposed anthers to feathery stigmas
45
What travels down pollen tube
Pollen nucleus
46
What is fertilisation in plants
Fusion of pollen nucleus and ovum nucleus to form zygote
47
What does ovule become after fertilisation
Seed
48
What does ovary become after fertilisation
Fruit
49
Why do plants form fruits
To help seed dispersal
50
Example of seed dispersal by animals
Fruit eaten seeds dispersed in droppings
51
Another seed dispersal adaptation
Sticky hooks catch on animal fur
52
What is a micropyle?
Small opening in surface of ovule
53
What conditions are required for germination?
Water (swells seed, breaks seed coat, activates enzymes for growth) Oxygen (respiration) Warmth (enzyme activity)
54
Describe method for "Conditions for germination" practical
Prepare 4 test tubes with 10 cress seeds on cotton wool Tube A: Keep wool dry, warm Tube B: Moisten wool, warm Tube C: Cover seeds and wool with water and add layer of oil (so no oxygen dissolves into water), warm Tube D: Moisten cotton wool and place tube in fridge Leave for 3-5 days but make sure tubes B, D stay moist Compare number of germinated seeds
55
What do plant seeds contain?
Embryo shoot Embryo root Seed leaves (cotyledons) Food store (starch + other nutrients)
56
How does natural asexual reproduction in plants occur
Some plants grow side branches (runners) with small plantlets at ends Plantlets grow roots whenn they touch the soil and become independent from parent ## Footnote Genetically identical
57
How to clone a plant using cuttings
New bud is cut off Placed into water until new roots grow or sometimes placed directly in soil Sometimes stem of cutting is first dipped into "rooting powder" containing rooting hormones
58
What is the function of the sperm duct
Carries sperm mixes with gland fluids before entering urethra
59
What is the function of the urethra
Tube in penis carries urine or semen (ring of muscle stops mixing)
60
What is the function of the testis
Produces sperm and testosterone
61
What is the function of the scrotum
Sac holding testes outside body keeps sperm cooler than body temp
62
What is the function of the penis
Passes urine out and delivers semen into vagina during intercourse
63
What is the function of the oviduct
Connects ovary to uterus lined with cilia (pushes ovum) fertilisation occurs here
64
What is the function of the ovary
Contains ova female gametes matures when hormones released
65
What is the function of the uterus
Muscular bag soft lining where zygote implants and foetus develops
66
What is the function of the cervix
Ring of muscle at uterus base keeps foetus in place during pregnancy
67
What is the function of the vagina
Muscular tube receives penis deposits sperm during intercourse
68
Around which day does ovulation occur?
14
69
What occurs if the egg is not fertilised (human reproduction)
Uterine lining (endometrium) breaks down and is shed through vagina (menstruation lasts around 5-7 days and start of it is start of next cycle)
70
What occurs after menstruation
Uterin lining thickens again (in response to hormones) preparing for the possible implantation of fertilised egg (cycle restarts)
71
What is the role of oestrogen in the menstrual cycle?
Stimulates uterus to develop a lining Post-ovulating inhibits FSH and LH production in the pituitary gland
72
Role of progesterone in menstrual cycle
Maintains and thickens lining of the uterus Inhibits FSH and LH production If fertilisation doesn't occur, levels drop and menstruation occurs
73
Describe the graphs of Oestrogen and Progesterone in the menstrual cycle
Oestrogen - Rises to peak at day 14. Then falls, little bump from day 14 to 28 Progesterone - Large bump from day 14 to day 28 | Bump is fully contained by the two dates
74
Role of FSH (menstrual cycle) ## Footnote Follicle-stimulating hormone
Stimulates egg maturation in the follicles of ovary Stimulates follicles in the ovaries to secrete oestrogen
75
Role of LH (menstrual cycle) ## Footnote Luteinising hormoone
At its peak stimulates ovulation Results in the formation of a corpus luteum
76
On which day do FSH and LH peak?
Day 14
77
How do FSH LH oestrogen and progesterone interact in menstrual cycle?
FSH from pituitary stimulates follicle growth follicle makes oestrogen which thickens uterus lining and inhibits FSH high oestrogen triggers LH surge causing ovulation follicle becomes corpus luteum making progesterone which maintains lining if no fertilisation corpus luteum breaks down, progesterone falls, lining sheds if pregnant corpus luteum and later the placenta keep progesterone high
78
What is the placenta
Structure at implantation site connects mother and fetus for exchange
79
What does placenta provide to fetus
Oxygen and nutrients like glucose amino acids vitamins minerals
80
What does placenta remove from fetus
Carbon dioxide and urea
81
Do mother and fetus blood mix
No blood supplies stay separate
82
What connects fetus to placenta
Umbilical cord
83
Why is placenta efficient exchange surface
Large surface area thin walls for diffusion
84
What else does placenta do
Acts as barrier to some toxins and pathogens
85
What can cross placenta despite barrier
Nicotine alcohol viruses
86
What is amniotic fluid
Fluid in amniotic sac around embryo cushions and protects during development
87
Examples of female secondary sexual characteristics
Breast development wider hips body hair menstrual cycle starts
88
Examples of male secondary sexual characteristics
Growth of penis and testes facial and body hair muscle growth voice breaks sperm production starts
89
What is the genome
the entirety of an organism's DNA
90
What is a gene?
A section of a molecule of DNA
91
when is the only time chromosomes are visible
during cell division
92
What is each pair of chromosomes called
Homologous pair
93
In each homologous pair, how many chromosomes are inherited from each parent
1
94
What does each gene do?
Code for a protein
95
Full name of DNA
deoxyribonucleic acid
96
What are the DNA strands formed from?
sugar phosphate backbone with bases: A T G C
97
98
What is the genome?
The entirety of an organism's DNA
99
What is a gene?
A section of a molecule of DNA that codes for a protein
100
What is a pair of chromosomes called?
Homologous pair
101
How many chromosomes in a homologous pair come from each parent
1
102
Full name of DNA
deoxyribonucleic acid
103
What are DNA strands formed from
Sugar phosphate backbone with bases: A T G C
104
What are the complementary base pairings?
A->T G->C
105
RNA full name
ribonucleic acid
106
what is a polynucleotide
made up of many nucleotides (RNA, DNA is this)
107
What makes up a nucleotide?
Phosphate, sugar, base
108
What bases are in RNA?
A G C U (Replaces T)
109
Are RNA molecules single or double stranded?
Single
110
Differences between RNA and DNA
RNA is single stranded RNA contains U instead of T
111
What are the 2 stages of protein synthesis
Transcription Translation
112
Describe transcription in protein synthesis
Occurs in nucleus DNA->mRNA 1. DNA unwinds when hydrogen bonds between complementary base pairs break 2. Exposes template strand 3. Free mRNA nucleotides bind to complementary nucleotides on template 4. mRNA nucleotides join to neighbours -> 1 strand of mRNA 5. leaves nucleus
113
When is the only time DNA is visible
during cell division
114
What from is DNA in during interphase
Chromatin
115
Describe protein translation
Occurs in cytoplasm 1. mRNA attaches to a ribosome 2. free molecules of tRNA in cytoplasm. Anticodons pair with codons, bringing each amino acid into place. 3. peptide bonds formed between amino acids 4. this continues until 'stop' codon reached
116
What is the anticodon
Triplet of unpaired bases at one end of tRNA molecules
117
What is an allele
Alternative forms of the same gene
118
What is the phenotype?
The observable characteristics of an organism
119
What is the genotype?
The combination of alleles an organism has for a particular gene Aa AA aa
120
What are the 2 types of allele
Dominant Recessive
121
Homozygous
AA aa homo - same
122
Heterozygous
Aa hetero - different
123
What is codominance?
When both alleles within a genotype are expressed in the phenotype
124
What are polygenic characteristics?
Characteristics controlled by more than one gene
125
WHat is polygenic inheritence
Inheritance of polygenic characteristics
126
What are the symbols and meanings in family pedigrees
Square: Male Circle: Female Red: Affected Blue: Unaffected
127
What determines sex?
XX - female XY - male
128
What is mutation
A rare, random change that occurs in the sequence of DNA bases in a gene
129
Can mutations be inherited
yes
130
How much do most mutations alter the protein or its function
Not much
131
Haploid and diploid number in humans
46 23
132
How can a change in DNA affect the phenotype
Altering sequence of amino acids
133
What are the 3 ways to change the sequence of DNA?
Insertion, deletion, substitution
134
What is an insertion
New base randomly inserted into DNA sequence Changes that codon and all those down the line
135
What is a deletion
Base is randomly deleted from DNA sequence Changes that codon + knock-on effect
136
What is a substitution mutation
Base randomly swapped in DNA sequence Only changes that codon
137
What can mutations occasionally create?
New alleles, which may lead to new phenotypes.
138
When is a new mutation more likely to be passed on to future generations?
When the new phenotype provides a survival or reproductive advantage.
139
Example of a mutation that gives a reproductive advantage.
A mutation that changes a bird’s feather colour, making it more attractive to mates.
140
Can mutations be harmful?
Yes — some mutations cause significant health problems.
141
Example of a harmful mutation.
Sickle cell anaemia, caused by a mutation in the gene coding for haemoglobin.
142
Do mutations happen often?
Yes — they occur spontaneously and continuously.
143
What factors increase the mutation rate?
Ionising radiation (gamma rays, X-rays, UV) and chemical mutagens (tar)
144
How do ionising radiations increase mutation rate?
They damage DNA by breaking chemical bonds and altering base sequences.
145
What can higher mutation rates lead to?
Cells becoming cancerous, increasing cancer risk.
iGCSE Edexcel Biology
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