AQA A Level Biology复习笔记8.2.1 Totipotent Cells
Totipotent Cells A?stem cell?is a cell that can?divide?(by mitosis) an?unlimited number of times Each new cell that is produced when a stem cell divides has the potential to?remain a stem cell?or t...
AQA A Level Biology复习笔记8.1.1 Genetic Mutations
Gene Mutations A?gene mutation?is a change in the sequence of base pairs in a DNA molecule that may result in an altered polypeptide Mutations occur?continuously?and?spontaneously Errors in the DNA...
AQA A Level Biology复习笔记7.4.1 Communities
The Definition of a Community Species?do not exist by themselves in their own isolated environment, they interact with other species forming?communities A community can be defined as: Multiple popu...
AQA A Level Biology复习笔记7.3.1 Genetic Variation
Genetic Variation Phenotype variation The observable characteristics of an organism are its phenotype Phenotypic variation is the?difference in phenotypes?between organisms of the same?speci...
AQA A Level Biology复习笔记7.2.1 Populations
Species Exist in Populations A?species?can be defined as a group of?similar organisms?that can?reproduce?to give?fertile offspring Organisms of the same species have the?same number of chromosomes?...
AQA A Level Biology复习笔记7.1.1 Key Terms in Genetics
Key Terms in Genetics Genes & alleles The DNA contained within chromosomes is essential for cell survival Every?chromosome?consists of a long DNA molecule which?codes for several differe...
AQA A Level Biology复习笔记6.4.1 Principles of Homeostasis
Homeostasis In order to?function?properly and?efficiently, organisms have different?control systems?that ensure their?internal conditions?are kept relatively?constant Physiological control systems ...
AQA A Level Biology复习笔记6.3.1 Muscle Pairs
Muscle Pairs The?effective movement?of the human body requires both?muscle?and an?incompressible skeleton This is because muscles will only produce effective movement if they?pull on a structure?th...
AQA A Level Biology复习笔记6.2.1 Neurones
Myelinated Motor Neurones Information is sent through the nervous system as?nerve impulses?– electrical signals that pass along nerve cells known as?neurones A bundle of neurones is known as a nerv...
