Unit 2: AoS2 Flashcards
Fission
A single unicellular parent organism divides into 2 approximately equal parts that become new individuals.
Budding
- An outgrowth or bud that forms from the parent and becomes a new individual
- Cytoplasm is unevenly split
EXAMPLES: yeast, hydra, sponges
Fragmentation
- Multicellular parent body breaks into 2 parts which each develop into a new individual.
- Works best in organisms with simple body systems or ones that are spread throughout the body
EXAMPLES: flatworms, echinoderms, marine worms
Spore formation
- Spores are formed by mitosis.
- Capable of germinating into a new organism.
- Coated in a tough outer layer to help them survive harsh conditions.
EXAMPLES: mould, moss, ferns
Vegetative propagation
New plants develop from the roots, stems or leaves of parent plant.
EXAMPLES: strawberry runners
Parthenogenesis
- The development of a female gamete without fertilisation.
- Only possible in female parent organisms.
- This is in organisms that can still produce sexually.
EXAMPLES:komodo dragons, geckos, hammerhead sharks
Advantages of asexual reproduction
- Efficient reproduction
- Uses less time and energy
- Can increase population size rapidly in optimal conditions
- No need to find sexual partner
- Offspring are well suited to environment as are genetically identical
Disadvantages of asexual reproduction
- Overcrowding and competition for resources if population growth is too rapid
- Susceptible to environmental change
Sexual reproduction
Fusing of 2 gametes- haploid cells with half the number of chromosomes to form a new individual that is genetically different to its parents
Advantages of sexual reproduction
- Each gamete is genetically unique with a different combination of alleles
- This allows population to adapt and survive changing environments
- Quality over quantity- can eliminate undesirable traits
Disadvantages of sexual reproduction
- Slower reproduction
- Recombination may break apart desirable alleles
- Requires mating partner
- Takes more time and energy
Cuttings and grafts
Cuttings
- taking a section of a mother plant and it will grow into a clone
Grafts
- part of a stem from one plant is transferred to the rootstock of another plant
Tissue culture
- Fragments or single cells are selected from a parent plant and grown in a nutrient and hormone rich culture medium.
- Grows into plantlets which are clones of the parent plant.
Embryo splitting
- Based on the natural embryo splitting that forms identical twins.
- IVF is used to harvest eggs then fertilise in a petri dish.
- Embryos are split in early stages of development and implanted into surrogates.
Somatic cell nuclear transfer
Nucleus is removed from an unfertilised egg and replaced with the nucleus from an adult somatic cell. The egg is then transplanted into a surrogate. The offspring will be identical to the donor of the somatic cell.
Issues with cloning
- Susceptibility to disease
- High failure rate
- Adverse health effects
- Premature ageing
- Cloned food products may contain allergens
Gene pool
All genes and alleles in an interbreeding population
Selective advantage
Advantages in a species in a specific area
Genetic flow
Migration leading to new genes and alleles in a gene pool
Founder effect
Organisms arriving in a place they weren’t previously
Bottleneck effect
Small amounts of a population left, affects randomly, shrinking gene pool. e.g seasonal climate change, heavy predation/ disease, natural disaster
Genetic equilibrium
A theoretical point where all members of a population have an equal chance of contributing to the gene pool
Causes of genetic variation
- Mutations (different genetic sequences) causing genotypic changes, therefore phenotypic changes
- Sexual reproduction through independent assortment and crossing over
- Environmental factors interacting with genes
- Selection pressures
Genetic drift
Change in frequency of alleles from generation to generation caused by chance
Process of natural selection
- Variation of a trait in a population
- Struggle for survival/ selection pressure
- Survival advantage
- Reproduction from surviving individuals makes advantageous trait more common
Fragmented population
Populations separated by things like habitat loss
Consequences of low genetic diversity
- Loss of evolutionary potential and increased risk of extinction
- Inability to adapt to new environmental climate
- Disease
Inbreeding depression
Types of adaptations
- Structural- anatomy
- Physiological- bodily functions
- Behavioural- organisms activity
Abiotic factors
The non-living factors that impact on the survival of an organism in its environment
EXAMPLES: water, temperature, pH, salinity
Biotic factors
The living factors that impact on the survival of an organism in its environment
EXAMPLES: competition, predators, parasites
Tropisms
- Growth response- physiological
- Positive tropism- towards stimulus
- Negative tropism- away from stimulus
EXAMPLES: phototropism, geotropism, chemotropism, thigmotropism, hydrotropism
Nastic movements
Movement in response to environmental stimulus, but is independent from direction of stimulus. e.g photonasty, thigmonasty, thermonasty
Counter-current exchange
Physiological adaptation often present in flippers, feet, tails of marine animals. Cold blood (in veins) passes by warmer blood (in arteries) thus absorbing heat through concentration gradient. The heated blood travels back to the heart maintaining body temp.
Camoflage
Physiological- Animals blend in with certain aspects of their environment to increase chance of survival either to hide from prey or prey so they get close to you.
Bioluminescence
Physiological- Light is produced as a result of a chemical reaction to attract attention, lure prey or frighten predators
Torpor
Physiological- Organism lowers its metabolic rate to save energy, usually to survive difficult conditions, like cold or lack of food. Hibernation- prolonged period of torpor over winter
Aestivation- prolonged period of torpor over summer to survive high temperatures and scarce water
Adaptations in arid environments
- Evaporative cooling behaviours
- Basking in the sun
- Seeking shade/ shelter
- Living in a burrow
- Nocturnal activity
Individual
One of a species
Population
All individuals of a species in a specific location
Community
All populations of species in a specific location
Ecosystem
All living and non-living things in a specific location
Biome
Type of ecosystem e.g desert, rainforest
Niche
The role of a species in an ecosystem. It consists of:
- It’s role in the ecosystem e.g herbivore
- It’s tolerance limits
- It’s requirements for shelter, nesting sites throughout the year
If there is too much overlap in species niches, they leave or evolve
Symbiosis
A close and long-term biological relationship between 2 different biological organisms.
Mutualism
Both partners benefit
Obligate: each species is entirely dependant on the other
Facultative: Each species benefits, but not needed for survival
Commensalism
One organism benefits while the other is unaffected
Parasitism
A non-mutual relationship between 2 organisms. One species, the parasite benefits at the expense of the host
Amensalism
An individual species harms another without obtaining benefit- accident
Predation
A predator (hunting organism) feeds on its prey
Keystone species
An organism that plays a unique and crucial role in maintaining the structure of a community. Without them, the ecosystem would be very different or not exist
Processes affecting population size
- Natality
- Mortality
- Immigration
- Emigration
Adaptations in arctic environments
- Huddling
- Migration- moving large distances to seek better food availability or breeding grounds
