GCSE AQA Combined Science: Trilogy Biology Paper 2 Revision Notes

Flashcards on B10-B17 Topics (Human Nervous System, Hormonal Coordination, Reproduction, Variation and Evolution, Genetics and Evolution, Adaptations, Interdependence and Competition, Organising an Ecosystem, Biodiversity and Ecosystems)

What is homeostasis?

The regulation of the internal conditions of a cell or organism to maintain optimum conditions for function in response to internal and external changes.

Name three conditions controlled by homeostasis in the human body.

Blood glucose concentration, body temperature, and water levels.

What three components are included in all control systems for homeostasis?

Receptors, coordination centers, and effectors.

What is the role of receptors in a control system?

To detect stimuli (changes in the environment) and pass information to coordination centers.

What is the role of effectors in a control system?

Muscles or glands that bring about responses to restore optimum levels.

What is the difference between nervous responses and chemical responses in homeostasis?

Nervous responses are produced by the Central Nervous System, while chemical responses are produced by the Endocrine System.

List three examples of coordination centers.

Hypothalamus (Brain), Spinal Cord, or Pancreas

List three types of effectors

Arm or Leg Muscles, Adrenal Gland or Thyroid Gland

What is function of the nervous system?

To enable humans to react to their surroundings and to coordinate their behavior.

What two components make up the Central Nervous System (CNS)?

The brain and spinal cord.

What is the pathway of a nervous response?

Stimulus ---> Receptor ---> Coordinator ---> Effector ---> Response

What is the role of a relay neurone, and in what type of action is it involved?

Carries electrical impulses, involved in Reflex Actions.

What are the three types of neurones?

Sensory Neurone, Relay Neurone, Motor Neurone

What is the function of a sensory neurone?

Impulses carried from the receptor to the central nervous system.

What is the function of a motor neurone?

Impulses carried from the relay neurone to the effector(s).

Describe how the structure of neurones are adapted to carry out their functions.

• Long (fibre) axon is extended and long enough to reach and transmit nerve messages between other cells and around different parts of the body. Covered with a fatty (myelin) sheath, which helps to insulate the cell and helps to speeds the transmission of nerve impulses around the body / between cells. Tiny branches (dendrons) reach further, which cover both ends of the nerve cell, and allows it to send and receive nerve impulses quicker between other cells

What is the difference between a conscious action and a reflex action?

A conscious action is a nervous response that occurs by a conscious decision made by a coordination center (brain), while a reflex action is an automatic and rapid nervous response that occurs quickly and without conscious decision.

In a reflex action, what is the coordination center?

The Spinal Cord (ONLY)

Define 'Reflex Arc'.

The nerve pathway of a reflex action, with the sensory, relay and motor neurones (respectively)

What is synapse?

Small gap found between the junction of two neurones, where nerve signals must cross

What is the role of the endocrine system?

System of glands that secrete chemicals (called hormones) directly into the bloodstream, where they are carried to a target organ to produce an effect. Compared to the nervous system, the effects are slower but longer lasting.

Which gland is considered the 'master gland' of the endocrine system?

Pituitary Gland

Name the components of the endocrine system and their corresponding roles.

• Pituitary Gland: Coordinates and controls secretion of hormones by other glands. - Pancreas: Produces insulin and glycogen to control blood glucose concentration. - Thyroid: Produces and releases thyroxine to stimulate metabolic rate. - Adrenal Gland: Produces and releases adrenaline for ‘flight-or-flight’ response. - Ovary: Produce and release oestrogen in females. - Testes: Produce and release testosterone in males.

How does insulin control blood glucose levels in the body?

It causes glucose to move from the blood into the cells. In liver and muscle cells excess glucose is converted to glycogen for storage.

What is the cause of Type 1 diabetes, and how is it treated?

The pancreas fails to produce sufficient insulin. It is characterized by uncontrolled high blood glucose levels and is normally treated with insulin injections.

What is the cause of Type 2 diabetes, and how is it treated?

The body cells no longer respond to insulin produced by the pancreas. A carbohydrate controlled diet and an exercise regime are common treatments.

What is the role of glucagon in controlling blood glucose concentration?

If the blood glucose concentration is too low, the pancreas produces the hormone glucagon that causes glycogen to be converted into glucose and released into the blood.

What is secreted by Pancreas in-response to HIGH Blood Glucose Concentration, and what effects does it have?

Insulin = Secreted by Pancreas in-response to HIGH Blood Glucose Concentration. Moves glucose from blood into Cells (for respiration) or into Liver (to be stored as glycogen)

What is secreted by Pancreas in-response to LOW Blood Glucose Concentration, and what effects does it have?

Glucagon. Breaks down glycogen in Liver into glucose, that is release into bloodstream.

What is the role of testosterone in human reproduction?

Main male reproductive hormone produced by the testes, it stimulates sperm production.

Name the key hormones involved in the menstrual cycle, and describe their roles.

• Follicle stimulating hormone (FSH): Causes maturation of an egg in the ovary. - Luteinising hormone (LH): Stimulates the release of the egg. - Oestrogen : thickens the uterus lining. - Progesterone : Hormone that is involved in maintaining the uterus lining.

Describe the function of Follicle Stimulating Hormone (FSH).

Hormone that causes the maturation of an egg in the ovaries

Describe the function of Luteinising Hormone (LH).

Hormone that stimulates the release of the egg

Describe the function of oestrogen in the female Menstrual Cycle.

Hormone that thickens the uterus lining

Describe the function of progesterone the female Menstrual Cycle.

Hormone that is involved in maintaining the uterus lining.

Describe examples of hormonal methods of contraception

Oral Contraceptives: Hormones that inhibit FSH production, so eggs don’t mature. Injection, Patch or Implant: Slow release of progesterone to inhibit maturation/release of eggs

Describe examples of non-hormonal methods of contraception.

Barrier Methods: Prevent sperm from reaching egg (e.g. Condoms / Diaphragm). Intrauterine Devices: Prevent implantation of embryo or release a hormone to inhibit so. Spermicides: Chemical agents that kill or disable sperms in semen. Surgical Methods: Sterilising procedures of vasectomy (male) and Tubal Ligation (female). Abstinence: Act of not participating (abstaining from) sexual activity or intercourse

What is a fertility drug?

Chemical pharmaceutical used to aid in achieving fertility. In woman who cannot become pregnant due to lack of FSH or lack of LH, these chemicals can be given artificially as a fertility drug – to allow them to become pregnant (in the normal way).

What is the general process of In Vitro Fertilisation (IVF)?

Woman is given FSH and LH to stimulate maturation of several eggs. The eggs are collected from the mother. Eggs are fertilised by sperm from the father in the laboratory. The fertilised eggs develop into embryos. At the stage when they are tiny balls of cells, one or two embryos are inserted into the mother's uterus (womb)

What is the role of adrenaline in the body?

Chemical hormone produced by the adrenal glands during times of fear or stress. The effect of is that it Increases Heart Rate and so boosts Delivery of Oxygen and Glucose to Brain / Muscles. It may also temporarily divert some blood away from non-essential organs (e.g. digestive organs) to provide to muscles. The role of Adrenaline is to increase heart rate in-order to provide vital organs with ADDITIONAL oxygen/glucose to prepare for Fight-or-Flight Response.

What is the role of thyroxine in the body?

Chemical produced that stimulates the basal metabolic rate (meaning rate of required bodily processes), and plays a vital role of the body’s growth and development. It is produced by the Thyroid Gland. The role Thyroxine is to stimulate basal metabolic rate, and mainly controls the rate that oxygen and food products react to produce energy. This means it is crucial for most bodily processes (digestion, bone/brain development, etc.)

What is the difference between Mitosis and Meiosis?

Mitosis: Leads to cells that are genetically identical and Used for growth and repair. Meiosis: Leads to cells that are genetically non-identical and Used to produce gametes

What is Sexual Reproduction?

The process involving the fusion of the nuclei of two gametes (sex cells) to form a zygote (fertilised egg cell) and the production of offspring that are genetically different

What is Asexual Reproduction?

The process involving resulting in genetically identical offspring (clones) from one parent, involving only mitosis. There is no fusion of gametes or mixing of genetic information.

What is a Zygote?

Fertilized egg cell (results from the union of a female gamete, egg or ovum, with a male gamete, sperm)

What actions occur when a cell divides to form gametes?

Copies of the genetic information are made. The cell divides twice to form four gametes, each with a single set of chromosomes. All gametes are genetically different from each other

What is DNA?

Chemical that genetic material in the nucleus of a cell is composed of The structure of DNA should be described as: (Long) Polymer made up of Two Strands (that are Twisted / Coiled / Spiralled) forming a Double Helix

What is the function of a Gene?

Small section of DNA found on a chromosome (structures where DNA is contained). Genes code for a particular sequence of amino acids, to make a specific protein. Genes control our characteristics as they code for proteins that play roles in what our cells do

What is a Genome?

All the genetic material (of an organism)

What are the meanings of gamete, chromosome, gene and allele?

Gamete: Sex cells in animals and plants. Chromosome: Thread-like structures of DNA, carrying genetic information in the form of genes. Gene: Small sections of DNA found on a chromosome. Allele: Different versions of a particular gene.

What are the meanings of dominant, recessive, homozygous and heterozygous?

Dominant (Allele): In context of Alleles, dominant allele is always expressed, even if only one copy is present. Recessive (Allele): In context of Alleles, recessive alleles are only expressed if two are present (no dominants). Homozygous: Having two of the same alleles for a gene / trait / characteristic / disorder. Heterozygous: Having two different alleles for a gene / trait / characteristic / disorder

What are the meanings of genotype and phenotype?

Genotype: The combination of alleles that control each characteristic. Phenotype: The observable characteristics of an organism as a result of genes (e.g. eye colour, freckles)

What is a Gene Cross?

Diagram used to represent the alleles of the parent genotypes, and help predict the genotypes and/or the phenotypes of potential offspring between the two

What is Polydactyly?

Having extra fingers or toes, caused by a dominant allele

What is Cystic Fibrosis?

Disorder of cell membranes caused by a recessive allele.

How is sex determined?

In females the sex chromosomes are the same (XX). In males the chromosomes are different (XY)

Describe how the genome and its interaction with the environment influence the development of the phenotype of an organism.

Differences in the characteristics of individuals in a population is called variation and may be due to: the genes they have inherited (genetic causes). The conditions in which they have developed (environmental causes). A combination of genes and the environment.

What is a mutation?

Continuously occurring mutations can (very rarely) lead to a new phenotype, which if suited to the environment, can lead to a rapid change across an entire species

What is Evolution?

Change in the inherited characteristics of a population over time through a process of natural selection which may result in the formation of a new species

What is the 'Theory of Evolution by Natural Selection'?

The scientific concept that all species of living things have evolved from simple life forms that first developed more than three billion years ago, as suggested by scientist Charles Darwin

When is a new species formed?

A new species is formed when one species become so different in phenotype that they can no longer interbreed to produce fertile offspring.

What is Selective Breeding?

The process by which humans breed plants and animals for particular genetic characteristics: Selective breeding involves choosing parents of the PLANT/ANIMAL with the desired characteristic. Breed this PLANT/ANIMAL together. Choose the offspring with the desired characteristic and breed them together. Repeat / Continue over many generations until all the offspring show the desired characteristic.

What is Genetic Engineering?

The process which involves modifying the genome of an organism by introducing a gene from another organism to give a desired characteristic

What is the relationship between fossils and evolution?

Fossils are the preserved remains of a dead organism from millions of years ago. This support Darwin’s Theory, which states that simple life forms gradually evolved into more complex ones (as is shown)

What is MRSA?

an example of a bacteria resistant to antibiotics

How are living things classified?

living things have been classified into groups depending on their structure and characteristics in a system developed by Carl Linnaeus. Linnaeus classified living things into kingdom, phylum, class, order, family, genus and species. Organisms are named by the binomial system of genus and species.

What is the Linnaean System?

The system whereby living things are classified into groups depending on their structure and characteristics, developed by Carl Linnaeus. In the Linnean System, living things are classified according to: Kingdom, Phylum, Class, Order, Family, Genus, Species

What is the Three-Domain System?

System of classification based on evidence now available from chemical analysis, developed by Carl Woese. Using the Three-Domain System, organisms are divided into: Archaea (these are primitive bacteria usually living in extreme environments), Bacteria (organisms which are only true bacteria), Eukaryota (organisms which includes protists, fungi, plants and animals)

What is an Ecosystem?

The interaction of a community of living organisms (biotic) with the non-living (abiotic) parts of their environment.

List the Levels of Organisation in an Ecosystem

Individual, Population, Community, Ecosystem

What is Interdependence?

The concept that each species within a community depend on other species for different things (e.g. food, shelter, pollination, seed dispersal, etc.), and if one species is removed, it can affect the whole community

What is a Stable Community?

Community where all the species and environmental factors are in balance so that population sizes remain fairly constant

What are Abiotic Factors?

The non-living factors or aspects of a community or ecosystem

What are Biotic Factors?

The living factors or aspects of a community or ecosystem

What is an Adaptation?

The features of an organism that enable them to survive and reproduce most efficiently in the conditions in which they normally live. These adaptations may be of three different types: Structural, Behavioural, Functional

What is an Extremophile?

Organisms that live in environments that are very extreme, such as at high temperatures, high pressures, or areas with high salt concentration

Why are photosynthetic organisms considered the producers of biomass for life on Earth?

Photosynthetic organisms are the producers of biomass for life on Earth, because they produce their own food using energy from the Sun – which becomes biomass.

What is a Food Chain?

The relationship in how a consumer consumes another organism

What is a Predator?

Consumers that kill and eat other animals, who eat Prey (those that are eaten)

What is the Carbon Cycle?

The process that returns carbon from organisms to the atmosphere as carbon dioxide, whereby it is to be used by plants in photosynthesis

What is the process of the Water Cycle?

Water (vapour) enters into the atmosphere from both evaporates it from oceans/lakes/rivers (bodies) and Transpiration releases it from leaves and plants. Then the moist air rises very high, cools down, and this then condenses into liquid water (forming clouds). It then falls as precipitation (can be as rain/snow/hail).It then evaporates again, or is absorbed into earth via roots of plants/trees and returned to oceans by percolation, and Groundwater flow / run off also evaporates to the clouds

What is Biodiversity?

The variety of all the different species of organisms on earth, or within an ecosystem

How is waste controlled?

Unless waste and chemical materials are properly handled, more pollution will be caused. Pollution kills plants and animals which can reduce biodiversity

What is Deforestation?

The taking-down or removal of trees to clear an area of forest (for purpose of human activities)

Describe the biological consequences of human actions.

Ocean Temperatures Increasing (causing melting of polar ice caps / rising sea levels / flooding) Increasing Temperatures (causing extreme weather like super storms, flooding, droughts) Changes in or Loss of Habitats (caused by melting ice caps, flooding, sea levels and extreme weather) Decreases in Biodiversity (cause as food chains are disrupted and extinction rates increase by habitat loss)Increases in Migration of Species (caused by habitat loss, including increased spread of pests and disease)

List the Methods to Maintain Ecosystems and Biodiversity.

Breeding Programmes for Endangered Species,Protection and Regeneration of Rare Habitats,Reintroduction of Field Margins and Hedgerows for Farmers,Reduction of Deforestation and CO2 Emissions by Governments,Recycling Resources over Dumping Waste in Landfill