Adaptation & variation 2

Variation

Differences between individuals of the same species ;

Types of variation

Inherited variation and environmental variation ;

Inherited variation

Differences caused by genes passed from parents ;

Environmental variation

Differences caused by surroundings like diet, climate, lifestyle ;

How inherited variation is caused

Different alleles, gene combinations during fertilisation, mutations ;

How environmental variation is caused

Climate, diet, lifestyle, physical surroundings, other organisms ;

Definition of a species

A group of organisms that can reproduce to give fertile offspring ;

Why members of the same species look similar

They share many of the same genes ;

Breed (animals)

A group within a species with special inherited characteristics ;

Variety (plants)

A plant group within a species with special inherited traits ;

Ecosystem

All organisms and physical environmental factors in an area ;

Genetic information

Stored in DNA inside the nucleus ;

DNA

A molecule carrying genetic instructions for an organism ;

Chromosomes

Long strands of DNA found in the nucleus containing genes ;

Number of human chromosomes

46 chromosomes (23 pairs) ;

Genes

Sections of DNA that code for characteristics ;

Alleles

Different forms of the same gene ;

Dominant allele

Shows its effect even if only one copy is present ;

Recessive allele

Only shows if two copies are present ;

Example of dominant allele

Brown eye allele (B) ;

Example of recessive allele

Blue eye allele (b) ;

Genotype

The combination of alleles an organism has ;

Phenotype

The physical characteristics that appear ;

Punnett square

A diagram used to predict inheritance probabilities ;

Homozygous

Having two identical alleles (BB or bb) ;

Heterozygous

Having two different alleles (Bb) ;

Continuous variation

Range of values with no categories (height, weight) ;

Discontinuous variation

Clear categories with no in-between (blood group) ;

Data collection for variation

Measure characteristics, record in tables, analyse patterns ;

What fossils are

Preserved remains or traces of ancient organisms ;

Types of fossils

Imprints, casts, molds, mineralised bones, amber fossils ;

How fossils are formed

Organism dies → buried → decay → minerals replace parts → fossil forms ;

Limitations of fossil record

Incomplete, soft organisms rarely fossilise, fossils may be destroyed, not all found ;

Why the fossil record is incomplete

Geological activity, decay, erosion, lack of fossilisation ;

Selective breeding

Humans choosing parents with desired traits to produce useful offspring ;

How selective breeding works

Select parents → breed → choose offspring with best traits → repeat ;

Cross-breeding

Breeding two different breeds/varieties to combine characteristics ;

Advantages of selective breeding

Higher yields, better temperament, larger fruits, disease-resistant animals/plants ;

Disadvantages of selective breeding

Reduced genetic variation, health problems, inbreeding ;

Genetic engineering

Direct modification of an organism’s DNA using biotechnology ;

Examples of GM organisms

Insulin-producing bacteria, pest-resistant crops, golden rice ;

Adaptations

Features helping organisms survive in their environment ;

Behavioural adaptations

Actions an organism does to survive (migration, hibernation) ;

Structural adaptations

Physical features (fur, beaks, claws) ;

Physiological adaptations

Internal processes (sweating, venom, water conservation) ;

Adaptations in hot environments

Large ears, thin fur, nocturnal, water storage ;

Adaptations in cold environments

Thick fur, blubber, small extremities, white camouflage ;

Natural selection

The process where organisms with advantageous traits survive and reproduce ;

How natural selection works

Variation → competition → survival of the fittest → reproduction of best genes ;

Evolution

Change in species over time due to natural selection ;

Scientists who discovered natural selection

Charles Darwin and Alfred Russel Wallace ;

Example of natural selection

Faster jack rabbits survive better from predators ;

Why variation is important for survival

Provides options when environments change ;

Endangered species

Species at risk of becoming extinct ;

Causes of endangerment

Habitat loss, climate change, hunting, pollution, disease, competition ;

Extinction

When a species dies out completely ;

Ways to preserve biodiversity

Nature reserves, zoos, banning hunting, protecting habitats ;

Gene banks

Storage of seeds, sperm, eggs to preserve genetic material ;

Why biodiversity is important

Stability of ecosystems, medicine sources, food security, recovery from disasters ;

Competition in animals

Compete for food, mates, water, territory ;

Competition in plants

Compete for light, water, minerals, space ;

Symptoms of cystic fibrosis

Thick mucus, breathing difficulty, lung infections, digestive issues ;

Cause of cystic fibrosis

Mutation affecting chloride ion channels ;

Symptoms of sickle cell anaemia

Pain, fatigue, infections, sickle-shaped red blood cells ;

Cause of sickle cell anaemia

Faulty allele causing haemoglobin to deform ;

Symptoms of Huntington’s disease

Mood changes, loss of coordination, memory decline, uncontrolled movements ;

Cause of Huntington’s disease

Dominant faulty allele on chromosome 4 ;

Normal distribution curve

Bell-shaped curve showing continuous variation ;

Mutation

Random change in DNA that can create new alleles ;

Environmental factor examples

Sunlight, temperature, injuries, diet, living organisms ;

Interdependence

Organisms relying on each other in an ecosystem ;

Habitat

The environment where an organism lives ;

Survival of the fittest

The best-adapted individuals survive and reproduce ;

Reproduction

Process of producing offspring and passing on alleles ;

Inherited disorders

Disorders passed through genes, e.g., CF, sickle cell, Huntington’s ;

Asexual reproduction

Offspring identical to one parent (clones) ;

Sexual reproduction

Offspring receive genes from two parents → variation ;

Meiosis

Cell division forming gametes with half the number of chromosomes ;

Fertilisation

Joining of egg and sperm to form a zygote ;

Zygote

First cell of a new organism with full chromosome number ;

Gametes

Sex cells (sperm and egg) containing 23 chromosomes ;

Why offspring differ in sexual reproduction

Mixing of alleles from both parents ;

Why genetic engineering is faster than selective breeding

Direct DNA change instead of generations of breeding ;

Gene

A section of DNA controlling one characteristic ;

Genome

All genetic material of an organism