Unit 2: Multicellular Organisms Flashcards
(141 cards)
1
Q
Cell division (mitosis) is needed for:
A
Growth and repair
2
Q
Why must cell division produce identical cells?
A
So that the new cells have the correct chromosome complement
3
Q
Diploid cells
A
Diploid cells have two matching sets of chromosomes
4
Q
Chromosomes
A
X shaped structures found in the nucleus of cells that carry genetic information (genes)
5
Q
Chromosome structure
A
Two chromatids held together by a centromere
6
Q
Mitosis
A
A type of cell division
7
Q
Cell division stages:
A
-Chromosomes are not visible because they are uncoiled
-Chromosomes replicate to prepare for division
-Chromosomes coil up and become visible
-Nuclear membrane disappears, chromosomes line up on the equator
-Spindle fibres attach to the chromosomes
-Spindle fibres contract, chromatids are pulled apart and move to opposite poles of the cell
-The chromatids are now called chromosomes, nuclear membrane forms around each group of chromosomes
-Cytoplasm splits
-Two identical cells
8
Q
Disease caused by uncontrolled cell division
A
Cancer
9
Q
Stem cells
A
Unspecialised cells which can divide in order to self-renew, and have the potential to become different types of cells
10
Q
Uses of stem cells
A
Required for growth and repair of animal tissues
Can be used in leukaemia treatment and skin grafts for burns
11
Q
Types of stem cells
A
Embryonic— extracted from early stage embryos
Tissue— found throughout the body from birth to adulthood
12
Q
Why is the use of embryonic stem cells controversial?
A
Because it involves the destruction of embryos
13
Q
Cells show specialisation— what does this mean?
A
They have a special shape or structure which allows them to carry out a specific function
14
Q
Example of a specialised cell
A
Sperm cells have tails which allow them to swim to an egg cell
Root hair cells have a large surface area to help them absorb water
15
Q
Tissue
A
A group of specialised cells that work together to perform a particular function
16
Q
Organ
A
A group of tissues working together to perform a specific function
17
Q
Organ system
A
A group of organs working together
18
Q
Hierarchy of cells to organ systems
A
Cells — tissues — organs — organ systems — organisms
19
Q
Nervous system
A
The central nervous system (CNS) and other nerves
20
Q
Central nervous system (CNS)
A
Brain and spinal cord
21
Q
Parts of the brain
A
Cerebrum, cerebellum, medulla
22
Q
Cerebrum
A
Controls conscious thought and voluntary decisions
23
Q
Cerebellum
A
Controls balance and coordination
24
Q
Medulla
A
Controls heart rate and breathing rate
25
Stimulus
A change in conditions
26
Receptors
Receptors detect sensory stimuli
27
Types of neurons
Sensory neurons, inter neurons, motor neurons
28
Neurons
Carry messages in the form of electrical impulses
29
Sensory neurons
Pass information from receptors to the CNS
30
Inter neurons
Operate / process information within the CNS
31
Motor neurons
Enable a response to occur at an effector (muscle or gland)
32
Electrical impulses
Electrical impulses carry messages along neurons
33
Chemicals in neurons
Chemicals transfer messages between neurons at synapses (they diffuse across)
34
Reflex actions
Fast, automatic responses
35
Example of a reflex action
If your hand touches something hot, a message is passed along a sensory neuron, across an inter neuron and along a motor neuron, which causes your muscle to contract
36
Reflex arc
A pathway of neurons
37
Hormones
Chemical messengers
38
Where are hormones released from?
Endocrine glands, into the bloodstream
39
Target tissue
The tissue a hormone has its effect on
40
Hormone specificity
Target tissues have cells in their membranes with complementary receptors for specific hormones, so only that tissue will be affected by the hormone
41
Examples of hormones
Insulin, human growth hormone
42
Blood glucose and hormones
Hormones are involved in controlling blood glucose levels
43
Hormones involved in controlling blood glucose levels
Insulin and glucagon
44
Where are insulin and glucagon produced?
In the pancreas
45
Insulin
Released when blood glucose levels are high. Activates enzymes in the liver which turn glucose into glycogen, lowering blood glucose level
46
Glucagon
Released when blood glucose levels are high. Activates enzymes in the liver which turn glycogen into glucose, raising blood glucose level
47
Gametes in plants
Male gamete: pollen, produced by anthers
Female gamete: ovules, produced by ovaries
48
The chromosome complement of gametes is
Haploid
49
Pollination
The pollen in a flower is transferred from the anthers to the stigma of the same / another flower
50
Fertilisation
The fusion of the nuclei of two haploid gametes to produce a diploid zygote
51
Haploid
One set of chromosomes
52
Gametes in animals
Female: Egg, produced by ovaries
Male: Sperm, produced by testes
53
Gametes
Sex cells
54
Features of an egg cell
Large food store-- allows it to divide and grow after fertilisation
55
Features of a sperm cell
Has a tail so it can swim to the egg cell
56
Fertilisation in animals
The nucleus of the sperm cell fuses with the nucleus of the egg cell to produce a diploid zygote
57
Variation
The differences between members of the same species
58
Combining genes from two parents contributes to...
Variation
59
Continuous variation
Variation with a range of values (e.g. height)
60
Discrete variation
Variation with distinct values (e.g. blood type)
61
Polygenic traits
Characteristics controlled by more than one gene
62
Single gene traits
Characteristics controlled by one gene
63
Continuous variation is controlled by...
More than one gene (polygenic)
64
Discrete variation is controlled by...
One gene
65
Genes contain
Instructions to make proteins
66
Alleles
Different forms of a gene
67
Dominant alleles
Dominant alleles always show up in the appearance of an organism even if there is only one copy present in the gene pair. Dominant genes are represented with capital letters
68
Recessive alleles
Recessive alleles only show up in the appearance of an organism if they are paired with another recessive allele. Recessive genes are represented with lowercase letters
69
Phenotype
Describes the appearance of an organism
70
Genotype
Tells us which forms of the gene (which alleles) are present
71
Homozygous
Alleles are the same (e.g. RR or rr)
72
Heterozygous
Alleles are different (e.g. Rr)
73
P
Parental generation
74
F1
First generation (offspring of the parental generation)
75
F2
Second generation (offspring of the first generation)
76
Monohybrid cross
Used to track the inheritance of a gene through several generations
77
Why do plants need water?
Plants need water to carry out photosynthesis (water is a raw material of photosynthesis)
Water helps to keep plants upright
Water is important for transporting other materials such as minerals around the plant
78
How does water enter the plant?
Water enters the root hair cells via osmosis, the water is then transported in dead xylem vessels
79
Xylem vessels
Dead, hollow tubes that transport water in an upwards direction only
They are responsible for transporting water and minerals from the roots to the leaves
80
Lignin
A tough, woody substance
Xylem cells are lignified to withstand the pressure changes as water moves through the plant
81
Other functions of xylem
Made up of strong lignified tubes that help to support the plant
Mineral elements are absorbed from the soil and dissolved in water so they are transported by xylem
82
Stomata
Tiny pores which allow gas exchange and also allow water to leave the plant
83
Guard cells
Control the opening and closing of the stomata
84
Palisade mesophyll
Site of photosynthesis
85
Spongy mesophyll
Site of photosynthesis
86
Upper epidermis
Protects the leaf (creates a waxy cuticle to protect the leaf)
87
Lower epidermis
Protects the leaf
88
Leaf vein
Transports water and sugar around the leaf
89
Transpiration
The process of water moving through a plant and its evaporation through the stomata
90
When water reaches the xylem in the leaves, it continues to travel by...
Osmosis
91
Water moves through the leaf by...
Diffusion between the leaf cell walls
92
How is water used when it reaches the leaves?
Some water is used to carry out photosynthesis
Some water, however, is not used, and this water evaporates out of the leaf through the stomata
93
Factors that increase the rate of transpiration
Increasing temperature, increasing wind speed, increasing surface area, decreasing humidity
94
Every cell needs sugar to...
Release energy
95
Phloem
Living tissue that is involved in transporting sugar up and down the plant
In particular, sugar is transported to growing points which require a lot of food
96
Sieve plates
Found in phloem tubes, allow sugar to pass from one cell to the next
97
Companion cells
Controls sieve plates in phloem tubes
98
Importance of blood
Blood allows substances to be transported from one place to another
99
Role of oxygen in the body
Required to release energy from food
100
Where is oxygen carried from and to in the body?
From the lungs to all cells in the rest of the body
101
Carbon dioxide in the body
Waste product of respiration
102
Where is carbon dioxide carried from and to in the body?
From cells in the body to the lungs
103
Role of nutrients (e.g. glucose) in the body
Required to produce energy
104
Where are nutrients (e.g. glucose) carried from and to in the body?
From the small intestine to all cells in the rest of the body
105
What makes up blood?
Red blood cells, white blood cells, plasma
106
White blood cells
Part of the body’s immune system
107
Red blood cells
Involved in the transport of oxygen and carbon dioxide
108
Plasma
Pale yellow liquid part of blood, substances such as glucose and carbon dioxide dissolve in plasma and are carried around the body
109
What substance do red blood cells contain?
Haemoglobin
110
Role of haemoglobin
Picks up oxygen in the lungs; when oxygen binds to haemoglobin, a complex called oxy-haemoglobin in formed
Oxygen is released from oxy-haemoglobin in the tissues to be used for respiration
111
How are red blood cells specialised?
Biconcave shape increased their surface area and allows them to absorb oxygen quickly
They do not have a nucleus, this means that the cell has more room to contain haemoglobin
112
Pathogens
Disease-causing microorganisms (bacteria, viruses, fungi)
113
Two main types of white blood cell
Phagocytes, lymphocytes
114
Role of phagocytes
Carry out phagocytosis (engulf pathogens and digest them)
115
Role of lymphocytes
Produce proteins called antibodies which destroy pathogens
116
Antibody specificity
Each antibody is specific to a particular pathogen, different antibodies have different shaped receptor sites
The shape of the receptor site on an antibody is complementary to the shape of molecules on the surface of the particular pathogen
117
Stages of phagocytosis
Phagocyte engulfs pathogen
Pathogen ingested by powerful enzyme
Harmless pathogen pieces are released from the phagocyte
118
Types of blood vessels
Veins, arteries, capillaries
119
Arteries
Carry blood away from the heart
Thick, muscular walls to withstand high pressure
Narrow central channel
When the heart pumps blood into the artery, the pressure causes the walls to expand— this is what you feel as your pulse
120
Veins
Carry blood back to the heart
Thinner walls and wider central channel than arteries
The blood in veins is much lower pressure than the blood in arteries
Contain structures called valves which prevent the backflow of blood (blood can only flow in one direction through a valve)
121
Capillaries
Form networks at tissues and organs
Allow substances to be exchanged from the blood and the tissues
Thin walls to ensure that diffusion happens quickly
Some capillaries may have walls that are only one cell thick
Large surface area also allows diffusion to happen quickly
122
Muscle that makes up the heart
Cardiac muscle
123
Chambers in the heart
Upper chambers: right atrium, left atrium
Lower chambers: right ventricle, left ventricle
124
Vena cava
Carries deoxygenated blood from the body to the heart
125
Why do the ventricles have thicker walls than the atria?
Because they have to push blood much further
126
Pulmonary artery
Carried deoxygenated blood from the heart to the lungs
127
Pulmonary vein
Carries oxygenated blood from the lungs to the heart
128
Aorta
Carries oxygenated blood from the heart to the rest of the body
129
Tissues contain capillary networks to…
Allow the exchange of materials at cellular level
130
Oxygen and nutrients must be…
Absorbed into the bloodstream to be delivered to cells for respiration
131
Waste materials such as carbon dioxide must be…
Removed from cells into the bloodstream
132
Features of surfaces involved in the absorption of materials
Large surface area
Thin walls
Extensive blood supply
These increase the efficiency of absorption
133
Capillaries allow the body cells to…
Receive oxygen and remove carbon dioxide
134
Lungs
Gas exchange organs
Allow oxygen to enter the blood and carbon dioxide to be removed from the blood
This process is known as gas exchange and takes place in the alveoli
135
Alveoli
Tiny air sacs surrounded by many blood capillaries
Oxygen diffuses from the alveoli to the blood
Carbon dioxide diffuses from the blood to the alveoli
136
The digestive system is also known as
The alimentary canal
137
Two main purposes of the digestive system
Digestion (the breakdown of food particles)
Absorption of the nutrients from food
138
The small intestine
The location where nutrients from food are absorbed
139
Villi
(Singular is villus)
Small, finger-like projections found in the small intestine that allow it to absorb nutrients from food efficiently
140
Blood capillaries absorb
Glucose and amino acids
141
Lacteals absorb
Fatty acids and glycerol
