National 5 Biology(Unit 2): Cell, Reproduction, and Circulatory System Key Concepts

Cell

Basic unit of life

Tissue

Group of specialised cells that perform one function

Organ

Structure made up of several different tissues that perform different functions

System

Groups of organs which work together

Mitosis

Process of cell division where chromosomes duplicate and the cell divides

Stem Cell

Undifferentiated cell that can give rise to specialized cells

Diploid

Cells that contain two sets of chromosomes

Chromosome complement

Total number of chromosomes in a cell

Sperm

Male reproductive cell that has a tail for swimming to the egg

Red blood cell

Cell that contains haemoglobin and carries oxygen

Palisade mesophyll cell

Cell in leaves that contains chloroplasts for photosynthesis

Haemoglobin

Protein in red blood cells that carries oxygen

Mitochondria

Organelles that provide energy for cellular functions

Biconcave

Shape of red blood cells that increases surface area for oxygen transport

Chromosomes

Structures that contain genetic information, with 46 in normal human body cells

Cell division

Process by which new cells are produced

Specialised cells

Cells that have different structures to perform specific functions

Multicellular organisms

Organisms made up of more than one cell type

Growth

Increase in size due to the production of new cells

Repair

Process of fixing damaged tissues through new cell production

Replacement

Process of replacing dead or damaged cells

Chloroplasts

Organelles in plant cells that carry out photosynthesis

Energy

Capacity to do work, provided by mitochondria in cells

Chromatids

The replicated chromosomes that join up by a centromere.

Stem Cells

Unspecialised cells in animals which can divide to self-renew and have the potential to become different types of cells.

Embryonic Stem Cells

Stem cells obtained from very early stage embryos.

Tissue (Adult) Stem Cells

Stem cells found in the body throughout life.

Central Nervous System (CNS)

The part of the nervous system composed of the brain and the spinal cord.

Cerebrum

The part of the brain that controls conscious thoughts, reasoning, memory and emotions.

Cerebellum

The part of the brain that controls balance and movement.

Medulla

The part of the brain that controls heart rate and breathing rate.

Nerve

Groups of neurons that travel together forming a bundle of neurons.

Sensory Neurons

Neurons that pass information from the sensory organ to the CNS.

Inter Neurons

Neurons that operate within the CNS and process the information that requires a response.

Motor Neurons

Neurons that enable a response to occur at an effector (muscle or gland).

Synapse

Gaps between neurons where chemicals are released to transfer messages.

Receptor Cells

Cells that detect the sensory input/stimulus.

Effector

A part of the body that produces the response, which can be muscles (rapid response) or glands (slow response).

Reflex Actions

Actions that occur to protect the body from harm.

Reflex Arc

The circuit of the neurons that act to produce a reflex action.

Hormones

Hormones are chemical messengers which travel through the bloodstream.

Endocrine glands

Hormones are produced and released from endocrine glands, e.g. pancreas, testes, ovaries.

Target tissue

The target tissue has cells with complementary receptor proteins for specific hormones.

Insulin

Hormones involved in blood glucose control, produced by the pancreas.

Glucagon

Hormones involved in blood glucose control, produced by the pancreas.

Blood glucose control

Endocrine gland = PANCREAS; Target tissue = LIVER.

Type of message (Nervous Control)

Electrical.

Type of message (Hormonal Control)

Chemical.

Speed of response (Nervous Control)

Rapid.

Speed of response (Hormonal Control)

Slow.

Length of effect (Nervous Control)

Short.

Length of effect (Hormonal Control)

Long.

Gamete

Sex cells are called gametes.

Haploid

Gametes are haploid - they have 1 set of chromosomes (n).

Sperm cell

The male gamete, small in size, released in millions.

Egg cell

The female gamete, larger in size, released in one.

Oviduct

Site of fertilisation.

Ovary

Site of egg production.

Testes

Site of sperm production.

Fertilisation

Fertilisation is the fusion of the nuclei of the two haploid gametes to produce a diploid zygote.

Zygote

The fertilised egg cell is called a zygote.

Pollination

Pollination is the transfer of pollen from the anther to the stigma.

Sexual reproduction

Produces variation by creating offspring with a new combination of genes from both parents.

Discrete variation

A characteristic where measurements fall into distinct groups, controlled by single gene inheritance.

Continuous variation

A characteristic which shows a range of values between a minimum and a maximum, controlled by polygenic inheritance.

Examples of discrete variation

Hand used for writing, blood group, petal colour.

Examples of continuous variation

Body mass, root length of plant, milk yield of cow.

Number of genes in discrete variation

Controlled by a single gene.

Number of genes in continuous variation

Controlled by several genes.

Polygenic inheritance

Inheritance controlled by multiple genes.

Gene

Controls inherited characteristics, with each characteristic being controlled by two forms of a gene.

Allele

The different forms of a gene.

Dominant allele

An allele that will always show in an individual's appearance, represented by a capital letter.

Recessive allele

An allele that is hidden by a dominant allele, requiring two copies to express the characteristic.

Genotype

The set of alleles present in an organism, e.g., BB, Gg, rr.

Phenotype

The physical appearance of an organism's inherited characteristic, e.g., blue, green, brown eye colour.

Homozygous

Both alleles are the same, e.g., BB, bb.

Heterozygous

The alleles are different, e.g., Bb.

Monohybrid cross

A genetic cross to determine the genotypes and phenotypes of offspring from two parents.

P

Represents parents in genetic crosses.

F1

Represents the first generation of offspring.

F2

Represents the second generation of offspring.

Expected phenotype ratio

The predicted ratio of offspring phenotypes which may differ from the actual ratio due to random fertilization.

Observed phenotype ratio

The actual ratio of offspring phenotypes observed in a genetic cross.

Homozygous dominant x homozygous recessive

A genetic cross between individuals with two dominant alleles and two recessive alleles.

Heterozygous x heterozygous

A genetic cross between two individuals with different alleles for the same gene.

Heterozygous x homozygous

A genetic cross between an individual with two different alleles and an individual with two identical alleles.

P Genotypes

Ww x ww

P Gametes

W or w, w or w

Punnett Square

W w w Ww ww w Ww ww

F1 Phenotype

50% WHITE, 50% PURPLE

F1 Genotype

1Ww: 1ww

Parental generation to F2 generation cross

In mice, black fur is dominant.

P Genotype

BB x bb

F1 Gametes

B or b

F2 Phenotype

75% WHITE, 25% GREY

F2 Genotype

1BB: 2Bb: 1bb

Plant organs

Plant organs are roots, stems and leaves.

Photosynthesis

Photosynthesis is the process by which plants make food.

Photosynthesis equation

carbon dioxide + water = oxygen + glucose