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Goes over the topics for B5 and B6 in Combined Science, plus additional questions featured only in Triple Science.
What does the term “homeostasis” mean?
Homeostasis is the process by which living organisms maintain a stable internal environment despite changes in external conditions. This involves regulating factors such as temperature, pH, and concentration of ions to keep physiological processes functioning optimally.
What do receptor cells do?
Receptor cells detect changes in the environment and convert stimuli into electrical signals that can be processed by the nervous system.
Give 5 examples of stimuli.
Light, sound, temperature, pressure, chemicals.
Where will you find light receptors in the body?
Eyes, specifically in the retina.
Where will you find sound receptors in the body?
Ears, specifically in the cochlea.
Where will you find temperature / heat sensors in the body?
The skin, specifically in sensory nerve endings and in the hypothalamus.
Where will you find chemical receptors in the body (that detect chemical stimuli)?
In the nose, specifically in the olfactory epithelium, and on the tongue, particularly in taste buds.
Where will you find pressure receptors in the body?
In the skin, particularly in the dermis, and in various internal organs such as the blood vessels.
Neurones are involved in communication within the body. What is sent along a neurone?
Electrical impulses or signals.
Which neurone carries information from receptors to the CNS?
Sensory neurones.
Which neurone carries information from the CNS to the effectors?
Motor neurones.
What are “responses” carried out by?
Effectors.
What are two types of effectors?
Muscles and glands.
Muscles are effectors. What do they do to bring about a response?
They contract and relax to produce movement.
What is a synapse?
A synapse is the junction between two neurons, where the transmission of signals occurs through neurotransmitters.
How are hormones carried around the body?
Hormones are carried through the bloodstream to target organs and tissues.
Hormones travel in the blood to specific organs. What are these organs called where the hormones act?
Target organs or tissues.
What is the “master gland” in the body, that stimulates other glands?
The pituitary gland, located in the brain.
Which organ/gland is shaped like a leaf and releases insulin and glucagon into the blood?
Pancreas
What two hormones are released from the pancreas to control blood glucose levels?
Insulin and glucagon.
Which hormone from the pancreas reduces blood glucose level?
Insulin.
Which organ detects high levels of glucose in the blood?
Pancreas, specifically the beta cells.
Insulin reduces blood glucose level. What is the first stage in how it does this?
The pancreas releases insulin into the bloodstream.
Insulin reduces blood glucose level. What is the second stage in how it does this?
It stimulates the liver to convert glucose into glycogen.
Where is glycogen stored?
The liver.
Where is glucose converted to glycogen?
Glucose is converted to glycogen primarily in the liver.
Which hormone released from the pancreas increases blood glucose level?
Glucagon.
Glucagon increases blood glucose level. How does it do this?
Glucagon increases blood glucose levels primarily by stimulating the liver to convert stored glycogen back into glucose, which is then released into the bloodstream. Additionally, glucagon promotes gluconeogenesis, a process where the liver creates glucose from non-carbohydrate sources, further raising blood glucose levels.
Which hormone converts glycogen to glucose?
Glucagon.
What does the hormone FSH do?
Follicle-stimulating hormone (FSH) is produced by the pituitary gland and plays a crucial role in reproductive processes. In females, FSH stimulates the growth and maturation of ovarian follicles, which are essential for the production of eggs (ova), and it also promotes the secretion of estrogen from the developing follicles. In males, FSH is important for the regulation of spermatogenesis, which is the process of sperm production in the testes. By influencing both egg and sperm development, FSH is essential for fertility and the overall regulation of the reproductive system.
From day 4-14 of the menstrual cycle, what happens to the uterus lining?
During days 4 to 14 of the menstrual cycle, also known as the follicular phase, the uterus lining (endometrium) undergoes significant thickening and regeneration in response to rising levels of estrogen produced by the developing ovarian follicles. After menstruation, the endometrium rebuilds itself, increasing in thickness and becoming more vascularized and glandular to prepare for a potential implantation of a fertilized egg. Additionally, this phase culminates in ovulation, typically occurring around day 14, where a mature egg is released from the ovary, further highlighting the importance of the endometrial preparation for possible pregnancy.
Which hormone is responsible for the growth of the uterus lining?
Estrogen.
What does the hormone LH do?
Luteinizing hormone (LH) triggers ovulation in females and stimulates testosterone production in males, playing a key role in reproductive health.
What does ovulation mean?
Ovulation is the release of a mature egg from an ovarian follicle, occurring mid-menstrual cycle and signaling peak fertility.
On which day of the menstrual cycle does ovulation take place?
Ovulation typically occurs around day 14 of the menstrual cycle.
What are two disadvantages to the contraceptive pill?
The contraceptive pill can have disadvantages such as potential side effects, like nausea or headaches, and an increased risk of certain health issues, including blood clots. Additionally, it does not protect against sexually transmitted infections (STIs).
Where in a cell is most of the genetic information stored?
The nucleus.
Within the nucleus there are chromosomes. These normally come in _____
pairs.
What are chromosomes made from?
Chromosomes are made from DNA tightly coiled around proteins.
What is a gene?
A gene is a segment of DNA that codes for a specific protein or trait.
What is an allele?
An allele is a variant form of a gene that determines specific traits.
What is a dominant allele?
A dominant allele is an allele that expresses its trait even when paired with a different allele.
How many dominant alleles need to be present for it to be expressed?
Only one.
What is a recessive allele?
A type of allele that only expresses itself when an individual has two copies of the allele and no dominant allele for that gene.
What part of cells are affected by cystic fibrosis?
The chloride channels in the cell membranes.
If CC means NORMAL, what would be the genotype of someone with cystic fibrosis?
cc
CC: Homozygous dominant (individual without cystic fibrosis and not a carrier)
Cc: Heterozygous or carrier
cc: Homozygous recessive (individual with cystic fibrosis)
If the allele for cystic fibrosis is the letter c, what would the genotype be for ‘normal’ (no cystic fibrosis alleles and not a carrier)?
CC
CC: Homozygous dominant (individual without cystic fibrosis and not a carrier)
Cc: Heterozygous or carrier
cc: Homozygous recessive (individual with cystic fibrosis)
If the allele for cystic fibrosis is the letter c, what would be the genotype for a person with cystic fibrosis?
cc
CC: Homozygous dominant (individual without cystic fibrosis and not a carrier)
Cc: Heterozygous or carrier
cc: Homozygous recessive (individual with cystic fibrosis)
How would you describe the genotype cc?
CC: Homozygous dominant (individual without cystic fibrosis and not a carrier)
Cc: Heterozygous or carrier
cc: Homozygous recessive (individual with cystic fibrosis)
How would you describe the genotype Cc?
CC: Homozygous dominant (individual without cystic fibrosis and not a carrier)
Cc: Heterozygous or carrier
cc: Homozygous recessive (individual with cystic fibrosis)
How would you describe the genotype CC?
CC: Homozygous dominant (individual without cystic fibrosis and not a carrier)
Cc: Heterozygous or carrier
cc: Homozygous recessive (individual with cystic fibrosis)
What is the definition for “variation”?
Variation is defined as differences between individuals of the same species.
What is a mutation?
A change in the DNA sequence of a cell or chromosome. Mutations can be caused by mistakes during cell division or by exposure to environmental agents that damage DNA. They can be random and rare, but can sometimes be inherited.
Charles Darwin came up with the theory of evolution. He called it evolution by ______ ______
Evolution by natural selection
Organisms with variations that are an advantage are more likely to ___________ and ____________, passing these ___________ on to the next generation.
Organisms with variations that are an advantage are more likely to survive and reproduce, passing these traits on to the next generation.
What is the definition for “extinction”?
The permanent loss of all members of a species, meaning that the species no longer exists anywhere on Earth.
Extinction can occur due to various factors, such as changes in the environment, competition, predation, disease, or catastrophic events.
Species may become extinct if:
The environment changes too quickly for the species to adapt (e.g., due to climate change or habitat destruction).
A new predator is introduced, which hunts the species extensively.
A new disease spreads, to which the species has no immunity.
A competitor species outcompetes the species for resources like food or habitat.
A catastrophic event occurs, such as a volcanic eruption, asteroid impact, or major natural disaster.
These factors can act individually or together, accelerating extinction.
What is the process called when genes are transferred from one organism’s genome to another (to produce a desirable characteristic)?
Selective breeding.
The first step to genetic engineering is to cut the gene you want from the DNA. What protein is used to cut this gene?
Restriction enzyme
Restriction enzymes recognize specific sequences of bases in the DNA and cut at or near these sites, allowing the desired gene to be isolated.
Explain why farmers may want to grow genetically engineered plants.
Increased crop yield: Genetically engineered plants may produce higher yields, helping to feed a growing population.
Resistance to pests: Plants can be engineered to produce toxins (e.g., Bt toxin) that kill insects, reducing the need for chemical pesticides.
Resistance to herbicides: Crops can be made resistant to herbicides, allowing farmers to kill weeds without damaging the plants.
Tolerance to environmental conditions: Genetic engineering can make plants more resistant to drought, frost, or soil salinity.
Improved food quality: Plants can be modified to contain more nutrients (e.g., Golden Rice with increased vitamin A).
Reduced costs: Less need for pesticides, herbicides, or other treatments can reduce farming expenses.
State an economic advantage of genetically modified crops.
An economic advantage of genetically modified (GM) crops is that they reduce the need for expensive chemical pesticides and herbicides, lowering the costs of farming and increasing profitability for farmers. Additionally, higher crop yields can lead to increased revenue.
State a social advantage of genetically modified crops.
A social advantage of genetically modified (GM) crops is that they can help reduce food insecurity by increasing crop yields and improving nutritional content, such as adding vitamins to staple foods (e.g., Golden Rice with vitamin A), benefiting communities with limited access to diverse diets.
State an environmental disadvantage of genetically modified crops.
An environmental disadvantage of genetically modified (GM) crops is the possibility of genes escaping into wild populations or non-GM crops through cross-pollination. This can lead to unintended consequences such as the creation of "superweeds" resistant to herbicides or the loss of biodiversity.
State a social/moral disadvantage of genetically modified crops.
A social/moral disadvantage of genetically modified (GM) crops is that people may be forced to eat GM foods due to their availability or affordability, even if they are morally or culturally opposed to them. This raises concerns about personal choice and consent, especially in regions where GM foods become the primary food source due to economic or environmental pressures.
Another reason some people are concerned about GM crops is that the transplanted genes may s______ in to the w______
Another reason some people are concerned about GM crops is that the transplanted genes may spread into the wild.
What are fossils?
The remains or traces of organisms from the past (around millions of years ago), usually found in rocks. Fossils can include hard parts of organisms, such as bones, teeth, and shells, as well as impressions or traces left by organisms, like footprints or burrows. Fossils provide important evidence for the history of life on Earth.
Homo sapiens is the binomial name for which animal?
Homo sapiens is the binomial name for humans.
What system of classification did Carl Woese propose?
Carl Woese proposed the three-domain system of classification. This system divides life into three broad domains.
What are the three domains in the three-domain system of classification?
Bacteria
Archaea
Eukarya
Woese's system is based on differences in the genetic material (specifically ribosomal RNA) of organisms, and it was a major revision of the traditional five-kingdom system.
What is DNA made up of?
DNA (deoxyribonucleic acid) is made up of nucleotides, which are the building blocks of the molecule.
What three molecules make up a nucleotide?
Each nucleotide consists of three parts:
A phosphate group
A deoxyribose sugar molecule
A nitrogenous base (one of four types: adenine (A), thymine (T), cytosine (C), or guanine (G))
The structure of DNA is a double helix, where two strands of nucleotides are held together by hydrogen bonds between complementary nitrogenous bases (A pairs with T, and C pairs with G).
Which molecules join to each sugar molecule in a nucleotide?
In a nucleotide, the phosphate group and the nitrogenous base join to the sugar molecule (deoxyribose in DNA). Specifically:
The phosphate group attaches to the 5' carbon of the sugar molecule.
The nitrogenous base attaches to the 1' carbon of the sugar molecule.
These connections form the backbone of the DNA strand, with the sugar-phosphate structure repeating along the length of the molecule.
In DNA, what is an order of three bases joined together called?
In DNA, an order of three bases joined together is called a codon. Each codon codes for a specific amino acid during protein synthesis.
What do triple bases (triplet code) code for?
In DNA, triple bases (or a triplet code) code for a specific amino acid in a protein. Each triplet, known as a codon, corresponds to one amino acid in the sequence of a protein, or it can signal the start or stop of protein synthesis. This is a key part of the genetic code, where the sequence of nucleotides in DNA is translated into a sequence of amino acids to form proteins.
Which molecule copies the code from DNA (in the ribosomes)?
In the ribosomes, the molecule that copies the code from DNA is messenger RNA (mRNA).
mRNA is transcribed from the DNA in the nucleus and carries the genetic code to the ribosome, where it is used as a template to assemble amino acids into proteins during translation.
What shape do proteins usually take?
Proteins usually take a specific three-dimensional shape or structure that is crucial for their function. This shape can be described in four levels of structure:
Primary structure: The sequence of amino acids in a polypeptide chain.
Secondary structure: The folding of the polypeptide chain into shapes like alpha helices or beta pleated sheets, held together by hydrogen bonds.
Tertiary structure: The overall three-dimensional shape of the protein, formed by the folding of the secondary structures, stabilized by various interactions like ionic bonds, hydrogen bonds, and hydrophobic interactions.
Quaternary structure: Some proteins consist of more than one polypeptide chain, and their final structure involves the arrangement of these multiple chains.
This final shape is essential for the protein's specific function, such as enzyme activity, structural support, or transport.
State 3 functions of proteins.
Enzyme activity: Proteins act as enzymes, catalyzing biochemical reactions in the body (e.g., breaking down food or building molecules).
Structural support: Proteins provide structural support to cells and tissues (e.g., collagen in connective tissues or keratin in hair and nails).
Transport: Proteins help transport substances across cell membranes or through the bloodstream (e.g., hemoglobin carrying oxygen in red blood cells).
In tissue culture, what are the cells placed in to grow, and what chemicals does this container contain?
In tissue culture, the cells are placed in a culture medium that is typically kept in a sterile container (such as a petri dish or culture flask). The culture medium contains:
Nutrients (such as amino acids, sugars, and vitamins) to support cell growth.
Hormones (like auxins and cytokinins) to stimulate cell division and differentiation.
Salts to maintain the correct pH and osmotic balance for the cells.
Growth factors to encourage the cells to divide and grow.
This combination of chemicals allows the cells to replicate and form tissue in a controlled environment.
Taking cuttings and planting them will produce ____________ ___________ plants to the parent plant.
Taking cuttings and planting them will produce genetically identical plants to the parent plant.
What method of animal cloning is generally used by farmers to produce cloned offspring?
The method of animal cloning generally used by farmers to produce cloned offspring is somatic cell nuclear transfer (SCNT).
In this process:
The nucleus of a somatic cell (a body cell) from the animal to be cloned is removed.
The nucleus is then inserted into an egg cell from which the nucleus has been removed.
The egg cell is stimulated to divide and develop into an embryo, which is then implanted into a surrogate mother to grow and develop.
This method is used to produce genetically identical animals, such as cows with desirable traits for milk or meat production.
What is the major disadvantage of animal cloning?
The major disadvantage of animal cloning is that it can lead to health problems in the cloned animals. These may include:
Shortened lifespan: Cloned animals may have a reduced lifespan or suffer from premature aging.
Increased risk of diseases: Clones can be more susceptible to certain diseases or developmental disorders.
Ethical concerns: The cloning process can raise ethical issues regarding animal welfare and the potential for abuse in cloning practices.
These disadvantages make cloning a controversial and complex issue.
State the name of the book Charles Darwin wrote in 1859, which laid out his theory of evolution.
“On the Origin of Species”
Explain why Darwin’s ideas were seen to be controversial.
Challenge to religious beliefs: Darwin's theory of evolution by natural selection contradicted the traditional belief that species were created by a divine being in their present form. Many people, particularly in religious communities, felt that his ideas undermined the concept of creation as described in the Bible.
Human origins: Darwin's theory suggested that humans shared a common ancestor with other animals, which was a radical and uncomfortable idea for many, as it placed humans within the animal kingdom, challenging long-held views about human uniqueness and divine creation.
Lack of immediate evidence: At the time Darwin proposed his theory, there was limited fossil evidence to fully support the idea of gradual evolutionary change. His theory was based on observation and logic rather than direct physical evidence, leading to skepticism and debate.
Social and cultural implications: Darwin’s ideas had broader social and cultural implications, including challenging the established understanding of society, hierarchies, and race. The theory of natural selection was sometimes misused to justify social Darwinism, which promoted the idea that certain human groups were biologically superior to others.
What did Jean-Baptiste Lamarck argue about changes to an organism?
Jean-Baptiste Lamarck argued that changes to an organism could occur through the inheritance of acquired characteristics. According to Lamarck's theory:
Use and disuse: Lamarck believed that if an organism used a particular part of its body more, that part would become stronger or more developed. Conversely, if a part was not used, it would weaken or shrink over time.
Inheritance of acquired traits: He proposed that any changes or traits acquired during an organism's lifetime, such as the development of muscles through frequent use, could be passed on to offspring.
For example, Lamarck famously suggested that the long neck of giraffes evolved because their ancestors had to stretch their necks to reach higher leaves, and this acquired trait was then inherited by subsequent generations.
What discovery eventually supported Darwin’s ideas?
The discovery that eventually supported Darwin’s ideas was genetics, particularly the work of Gregor Mendel on inheritance. Mendel’s experiments with pea plants in the mid-1800s showed how traits are inherited through distinct units, now known as genes. This provided a scientific basis for understanding how variations in organisms are passed down from generation to generation, which is a key part of Darwin’s theory of natural selection.
Additionally, the discovery of DNA and the mechanisms of genetic variation provided further evidence for Darwin’s ideas. The understanding that genetic mutations can introduce variation, and that these variations can be inherited and selected for or against in a population, helped validate the process of evolution by natural selection.
Fossil evidence, the study of embryology, and the observation of species’ geographical distribution also played crucial roles in supporting Darwin’s theory over time.
Who was the first person to do genetic experiments with pea plants?
The first person to conduct genetic experiments with pea plants was Gregor Mendel. Mendel, an Austrian monk, conducted his groundbreaking experiments in the mid-19th century. He studied the inheritance of traits in pea plants, carefully tracking how characteristics such as flower color, seed shape, and pod color were passed from one generation to the next. His work laid the foundation for the field of genetics, although it was not widely recognized until after his death. Mendel's discovery of the basic laws of inheritance (now known as Mendelian genetics) provided important insights into how traits are inherited, which later supported the understanding of evolution.
Mendel established that characteristics in plants are determined by…?
Mendel established that characteristics in plants are determined by genes. He proposed that these genes come in different forms, called alleles, and that each organism inherits two alleles for each trait—one from each parent. The interaction between these alleles determines the organism's traits.
Mendel also established the Law of Segregation, which states that the two alleles for a trait separate during the formation of gametes (egg and sperm), and each gamete carries only one allele for each trait. When the gametes combine during fertilization, the resulting offspring inherit one allele from each parent. This explained the inheritance patterns he observed in his pea plant experiments.
How did Mendel conclude that hereditary units passed onto offspring?
Mendel concluded that hereditary units (now known as genes) passed onto offspring through his systematic experiments with pea plants. Here’s how he reached his conclusion:
Controlled Crosses: Mendel carefully cross-pollinated pea plants with different traits (e.g., tall vs. short, purple vs. white flowers) to study how these traits were inherited across generations.
Observed Inheritance Patterns: By tracking the traits of offspring over multiple generations, Mendel observed consistent patterns. For example, in the first generation (F1), all plants exhibited one of the parental traits, suggesting that one trait was dominant over the other. In the next generation (F2), the hidden trait reappeared in a specific ratio (approximately 3:1), indicating that traits could be passed on and remain unchanged through generations.
Laws of Inheritance:
Law of Segregation: Mendel concluded that each organism carries two hereditary units (alleles) for each trait, one from each parent. These units segregate (separate) during gamete formation, so each gamete carries only one allele for each trait.
Law of Independent Assortment: He also found that genes for different traits are inherited independently of each other, which explained the variety of combinations of traits in offspring.
By using these observations, Mendel concluded that characteristics are controlled by discrete units (genes), which are inherited according to predictable patterns, passing from parent to offspring.
Mendel concluded hereditary units can be either _____ or _____.
Mendel concluded that hereditary units can be either dominant or recessive.
Dominant alleles are expressed in the organism’s traits, even if only one copy of the allele is present (e.g., tall plants with one tall allele and one short allele will still be tall).
Recessive alleles are only expressed when two copies of the allele are present (e.g., a plant must inherit two short alleles to be short).
This distinction between dominant and recessive alleles helped Mendel explain the inheritance patterns he observed in his pea plant experiments.
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