Biology GCSE Unit 1.1 Revision

When an animal arrives on an island, it is often isolated from its relatives on the mainland. This isolation can lead to different environmental conditions and resources on the island, which may require the animal to adapt in order to survive and reproduce. Over time, these adaptations can accumulate and result in significant genetic and physical differences between the island population and its mainland relatives. Eventually, these differences may become so pronounced that the island population can be considered a new species.

Cystic Fibrosis is a genetic disorder that affects the respiratory and digestive systems. One of the main symptoms of this condition is the accumulation of thick, sticky mucus in the lungs and other organs. This mucus can obstruct the airways and impair lung function, leading to breathing difficulties, frequent lung infections, and persistent coughing. The mucus can also block the ducts of the pancreas, preventing the release of digestive enzymes and causing problems with nutrient absorption. Therefore, the presence of an accumulation of thick, sticky mucus is a characteristic symptom of Cystic Fibrosis.

Darwin's Theory of Evolution states that variation is a fundamental aspect of populations of organisms. This means that most populations of organisms contain individuals that have slight differences from one another. These variations can be in terms of physical traits, genetic makeup, or behavior. This variation is essential for natural selection to occur, as it allows certain individuals to be better adapted to their environment and have a higher chance of survival and reproduction. Over time, these advantageous traits become more common in the population, leading to evolutionary change.

The correct answer is Homeotherm, Lungs, Fur, Use Placenta and give birth to live young, Feed Young on milk. This is because mammals are homeotherms, meaning they can regulate their body temperature internally. They have lungs for respiration, fur for insulation and protection, use placenta to nourish their developing young, give birth to live young, and feed their young with milk produced by mammary glands.

Genotype refers to the genetic characteristics of an organism, including the specific combination of genes that an individual possesses. It encompasses the genetic information that determines an organism's traits and characteristics, such as eye color, height, and susceptibility to certain diseases. Genotype is distinct from phenotype, which refers to the observable physical characteristics of an organism.

The correct answer is "Homeotherm, Lungs, Feathers, Eggs with Hard Brittle Shells." This is because birds are homeotherms, meaning they can regulate their internal body temperature. They have lungs for respiration, feathers for flight and insulation, and lay eggs with hard brittle shells for reproduction. Gills are not a characteristic of birds, as they are adapted for terrestrial life and do not have aquatic respiration. Fur is also not a characteristic of birds, as they have feathers instead.

Darwin's theory of Evolution states that individuals with advantageous characteristics are more likely to survive the struggle for survival. This means that traits or features that provide an advantage in terms of adaptation, reproduction, or competition for resources increase the chances of survival and passing on these traits to future generations. This process leads to the gradual accumulation of advantageous traits in a population over time, resulting in the evolution of species.

Phenotype refers to the physical characteristics of an organism, which are determined by its genetic makeup and the influence of the environment. It includes observable traits such as height, eye color, and hair texture. These traits are the result of the expression of genes and their interaction with the environment. Therefore, the correct answer is "Physical Characteristics of an Organism."

Sickle cell anemia is a genetic disorder that affects red blood cells. The abnormal shape of these cells can cause them to get stuck in blood vessels, leading to blockages and reduced blood flow. This can result in severe pain, organ damage, and other complications. Therefore, the statement "They can block blood flow" is the correct answer as it accurately describes one of the symptoms of sickle cell anemia.

The correct answer is "Multicellular, Do not have Cell Walls, Do Not have Chlorophyll, Feed Heterotrophically." This accurately describes the characteristics of the kingdom Animalia. Animals are multicellular organisms, meaning they are made up of multiple cells. They do not have cell walls, which is a feature that distinguishes them from plants and fungi. Animals also lack chlorophyll, the pigment responsible for photosynthesis in plants. Instead of producing their own food, animals obtain nutrients by consuming other organisms, making them heterotrophs.

The correct answer is "Multicellular, Have Cell Walls, Have Chlorophyll, Feed Autotrophically." This answer accurately describes the characteristics of the Kingdom Plantae. Plants are multicellular organisms, meaning they are made up of multiple cells. They have cell walls, which provide structural support and protection for the cells. Plants also contain chlorophyll, a pigment that allows them to capture sunlight and carry out photosynthesis. By photosynthesizing, plants are able to produce their own food and are classified as autotrophs.

The main characteristic of the phylum "Chordata" is that animals in this phylum have a supporting rod running the length of their body. This supporting rod is called the notochord and it provides support and structure to the body. It is present in all members of the phylum at some stage of their life cycle, although it may be replaced by a backbone in some species. This distinguishing feature sets chordates apart from other animal phyla.

The correct answer is Kingdom, Phylum, Class, Order, Family, Genus, Species. This is the correct order of biological classification, known as the Linnaean system. It starts with the broadest category, the kingdom, and then narrows down to more specific categories such as phylum, class, order, family, genus, and finally species. This hierarchical system helps organize and categorize living organisms based on their characteristics and evolutionary relationships.

The correct answer is "Poikilotherms, Lungs, Dry Scales, Leathery Eggs". This is because reptiles are poikilotherms, meaning their body temperature fluctuates with the environment. They have lungs for respiration, dry scales that provide protection, and leathery eggs that can survive in a terrestrial environment. Gills and eggs that have to stay in water are not characteristics of reptiles.

Homozygous refers to a genetic condition where an individual has two identical alleles for a particular gene. In this case, the correct answer states that homozygous means when the two alleles are the same (e.g., BB). This means that both copies of the gene are identical, resulting in the expression of the same trait or characteristic.

Continuous and discontinuous are types of variation. Continuous variation refers to a range of values that can be measured and can vary within a population, such as height or weight. Discontinuous variation refers to distinct categories or traits that are either present or absent, such as blood type or eye color. These types of variation are important in understanding genetic inheritance and the diversity of traits within a population.

Darwin's Theory of Evolution suggests that organisms tend to produce more offspring than the environment can support. This is because the competition for limited resources and the presence of predators and other factors make it difficult for all the offspring to survive to adulthood. Therefore, most organisms produce more young than will ultimately be able to survive and reproduce, leading to a natural selection process where only the fittest individuals pass on their genes to the next generation.

Scientists place vertebrates into groups based on their reproduction methods. Oviparous refers to animals that lay eggs, such as birds and reptiles. Viviparous refers to animals that give birth to live young, such as mammals. These two terms describe different strategies for reproducing and are used to categorize vertebrates based on their reproductive behavior.

Heterozygous refers to a genetic condition in which an individual has two different alleles for a particular gene. In this case, the example given is Bb, where B and b represent two different alleles. This is in contrast to homozygous, where both alleles are the same (e.g. BB or bb). Having different alleles can result in variations in the phenotype or physical characteristics of an organism.

Continuous variation refers to a trait that can take on a range of values, with no distinct categories or breaks. In this case, height is an example of continuous variation because it can vary continuously from short to tall, with no clear cutoff points or categories. Gender and eye color, on the other hand, are examples of discontinuous or categorical variation, as they have distinct categories (male/female, blue/brown/green, etc.) with no intermediate values.

An alternate form of a gene is called an allele. Alleles are different versions of the same gene that can result in different traits or characteristics. Each individual inherits two alleles for each gene, one from each parent. The combination of these alleles determines the genotype and ultimately the phenotype of an organism. Therefore, allele is the correct answer as it accurately describes the alternate form of a gene.

The correct answer is "Unicellular, Have a Nucleus." This is because the kingdom Protoctista consists of mostly unicellular organisms, such as algae and protozoa, which have a distinct nucleus. These organisms are eukaryotic, meaning they have a true nucleus enclosed within a membrane. They exhibit a wide range of characteristics and can be found in various habitats, including freshwater, marine environments, and soil. Some members of the kingdom Protoctista are also multicellular, but the majority are unicellular with a nucleus.

Scientists place vertebrates into groups based on their thermoregulation methods, specifically whether they are hometherms or poikilotherms. Hometherms are animals that can maintain a relatively constant body temperature, regardless of the external environment. They have the ability to generate and retain heat internally. On the other hand, poikilotherms are animals whose body temperature fluctuates with the temperature of their environment. They cannot regulate their body temperature internally and rely on external sources of heat to warm up or cool down. These two categories help scientists classify vertebrates based on their ability to regulate body temperature.

The correct answer is "Unicellular, Have no Nucleus." Prokaryotes are single-celled organisms that lack a nucleus and other membrane-bound organelles. They have a simple cellular structure and their genetic material is not enclosed within a nucleus. Prokaryotes include bacteria and archaea, and they are characterized by their ability to adapt to various environments and their role in processes such as nutrient cycling and decomposition.

The definition of a species as organisms that produce fertile offspring has limitations because not all organisms reproduce sexually. Some organisms reproduce asexually, such as bacteria and certain plants. Additionally, some hybrids, which are the offspring of two different species, can be fertile and able to reproduce. This challenges the idea that species can be strictly defined based on their ability to produce fertile offspring.

Blood groups are an example of discontinuous variation because they are distinct categories that individuals can fall into. Each blood group is clearly defined and separate from the others, with no intermediate or overlapping categories. In contrast, body mass and IQ are examples of continuous variation, as they exist on a spectrum and can vary in a continuous and gradual manner.

When two heterozygous mice are crossed, the possible combinations of alleles for their offspring are BB, Bb, Bb, and bb. This is because the heterozygous mice have one dominant allele (B) and one recessive allele (b). The dominant allele (B) is represented by capital letters, while the recessive allele (b) is represented by lowercase letters. Therefore, the likely offspring for the alleles B and b would be BB, Bb, Bb, and bb.

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The correct answer is "Poikilotherm, Lungs as Adult - Gills as Young, Moist Skin with no Scales, Eggs have shells and have to stay in water." This answer accurately describes the characteristics of amphibians. Amphibians are poikilothermic, meaning their body temperature varies with the environment. They have lungs as adults and gills as young, allowing them to breathe both in air and water. They have moist skin without scales, which helps with respiration. Their eggs have shells and must be laid in water for proper development.

The environment is the main cause of different characteristics relating to environmental variation. This is because organisms adapt and develop certain traits based on the conditions and resources available in their environment. These traits can include physical characteristics, behavior, and physiological adaptations. The environment plays a crucial role in shaping the genetic makeup and phenotypic expression of organisms over time.

The correct answer is "Poikilotherm, Gills, Slimy Scales, Eggs with no shell that have to stay in water." This is because fish are poikilotherms, meaning they cannot regulate their own body temperature and their body temperature varies with the temperature of their environment. They have gills for respiration, slimy scales for protection, and lay eggs with no shell that have to stay in water for the development of the embryos.

The causes of different characteristics relating to genetic variation are mutation or reproduction. Mutation refers to changes in the DNA sequence, which can lead to the formation of new alleles and variations in traits. Reproduction, on the other hand, involves the combination of genetic material from two individuals, resulting in offspring with a unique combination of genes. Both mutation and reproduction contribute to genetic variation by introducing new genetic material or reshuffling existing genetic material, respectively.

Natural new features occur through random mutations. Mutations are changes in the DNA sequence that can result in new traits or characteristics in organisms. These mutations can happen spontaneously and randomly during DNA replication or due to external factors like radiation or chemicals. Some mutations may be beneficial and provide an advantage to the organism, allowing it to adapt and survive better in its environment. Over time, these mutations can accumulate and lead to the development of new features in a population.

Viruses are not classified in any of the five living kingdoms because they lack essential characteristics of living organisms. One of these characteristics is the presence of cytoplasm, which is the gel-like substance found within cells. Since viruses do not have cytoplasm, they cannot carry out the necessary metabolic processes to sustain life on their own. Instead, viruses rely on infecting and taking over the cellular machinery of host organisms in order to replicate and survive. Therefore, viruses are considered non-living entities that exhibit characteristics of life only when they invade and exploit host cells.

Scientists place vertebrates into groups based on their oxygen absorption methods, which include lungs, gills, and skin. This means that vertebrates can either breathe using lungs, gills, or their skin. By categorizing vertebrates based on their oxygen absorption methods, scientists can better understand their respiratory adaptations and evolutionary relationships.

According to Darwin's theory of evolution, populations do not generally increase rapidly in size. This implies that there must be considerable competition for survival between organisms. This competition arises due to limited resources and the need to adapt to changing environments. Organisms that are better suited to their environment and can outcompete others have a higher chance of survival and passing on their traits to the next generation. Therefore, the presence of competition is necessary to control the number of organisms and ensure the survival of the fittest.

The structure of the nucleus is described as the cell containing chromosomes, within which genes are located. This means that the DNA, which carries the genetic information, is organized into chromosomes within the nucleus. Genes, which are segments of DNA, are then located within these chromosomes. This organization allows for the efficient storage and transmission of genetic information within the cell.