Biology Unit 2 AT3 COMPLETE Flashcards

Asexual reproduction

A type of reproduction that does not require fusion of gametes; offspring arise from one parent and are genetically identical.

Clone

A genetically identical organism or cell produced through asexual reproduction.

Binary fission

Asexual reproduction in bacteria where circular DNA replicates and the cell divides into two identical daughter cells.

Budding

Asexual reproduction where a new organism develops through cell division from an overgrowth on the parent. Example: Hydra.

Fragmentation

Asexual reproduction where part of an organism breaks off and regenerates into a new individual. Example: starfish.

Parthenogenesis

Asexual reproduction without fertilisation; an unfertilised egg develops into a new individual. Example: zebra sharks.

Vegetative propagation

Asexual reproduction in plants where a new plant grows from part of a parent plant rather than a seed. Examples: strawberries and potatoes.

Spore formation

Asexual reproduction where spores are released and germinate into new individuals. Examples: fungi, ferns and mosses.

Sexual reproduction

Reproduction involving genetic contributions, in the form of gametes, from two parental sources.

Gamete

A specialised reproductive cell produced during sexual reproduction. In animals, gametes are eggs and sperm.

Gonad

A specialised reproductive organ that produces gametes. Females have ovaries; males have testes.

Germline cells

Specialised cells in the gonads that give rise to gametes.

External fertilisation

Fertilisation where gametes are released into an external environment and fertilisation occurs outside the body. Examples: frogs and fish.

Internal fertilisation

Fertilisation where sperm enters the female reproductive tract and fertilises the egg within the female's body. Examples: reptiles, mammals and birds.

Advantages of asexual reproduction

Large numbers produced quickly; ideal for stable environments; successful traits preserved; rapid repopulation; no mate or courtship required.

Disadvantages of asexual reproduction

Lacks genetic variation; environmental change may make the population poorly suited and cause it to die.

Advantages of sexual reproduction

Produces genetic variation; ideal for changing environments; its advantages outweigh disadvantages in the eukaryotic world.

Disadvantages of sexual reproduction

Energy needed to find and secure a mate; courtship is costly; mating signals attract predators; fighting for mates can cause injury or death.

Tissue culture

A laboratory technology where many identical plant clones are produced from a small amount of plant tissue containing meristem tissue.

Meristem tissue

Unspecialised, undifferentiated plant tissue containing cells capable of continued division and differentiation.

Embryo splitting

A fertilised embryo is split into two, producing genetically identical individuals. The offspring are identical to each other, not to either parent.

Nuclear transfer / Somatic Cell Nuclear Transfer (SCNT)

Reproductive cloning where the nucleus of an adult somatic cell is inserted into an enucleated egg cell.

Somatic cell

Any body cell that is not a gamete. Examples include skin, muscle and liver cells.

Somatic cell nucleus donor

The organism providing the adult body cell whose nucleus is used. The clone's genotype comes entirely from this donor.

Egg donor

The organism providing the egg cell, which is enucleated. The egg provides cytoplasm and mitochondrial DNA, not nuclear DNA.

Surrogate mother

The female that carries and gives birth to the cloned embryo. She is not the genetic mother.

Enucleation

The removal of the nucleus and nuclear DNA from an egg cell, leaving the cytoplasm intact.

Telomeres

Specialised protective structures at chromosome ends that shorten during cell division; shortened telomeres may cause premature ageing in clones.

Key difference: Embryo splitting vs SCNT

Embryo splitting: genotype comes from both parents. SCNT: genotype comes from one somatic cell donor.

Cloning and genetic variation

Cloned animals lack genetic variation from each other, making the population vulnerable to diseases because resistance varies little.

Biodiversity

The total variety of life forms, their genes and the ecosystems of which they are part.

Genetic diversity

The variety of different alleles within a population of a species.

Species diversity

The number of different species living in a particular area or region.

Ecosystem diversity

The variety of different ecosystems and habitats in a region or on Earth.

Three levels of biodiversity

Genetic diversity: alleles; species diversity: species in an area; ecosystem diversity: ecosystems and habitats.

Mutation as source of variation

Mutations create new alleles, providing genetic variation that helps populations survive environmental change.

Adaptation

A genetically inherited structural, behavioural or physiological characteristic that enhances survival in particular environmental conditions.

Structural adaptation

A physical feature or body structure that helps an organism survive in its environment.

Physiological adaptation

A bodily process or mechanism that helps an organism function and survive in its environment.

Behavioural adaptation

A pattern of behaviour or action that enhances an organism's survival in its environment.

Habitat

The natural home or environment of an organism, providing food, water, shelter and space.

Biotic factors

Living things in a habitat, including predators, prey, competitors, parasites and plants.

Abiotic factors

Non-living things in a habitat, including temperature, light, water, soil, humidity, oxygen and pH.

Tolerance range

The extent of variation in an environmental factor within which a species can survive.

Optimum range

The range of environmental conditions where an organism thrives and reproduces successfully.

Zone of physiological stress

The range where an organism can survive but is stressed and not thriving.

Zone of intolerance

Environmental conditions so extreme that an organism cannot survive.

Tolerance limits

The upper and lower limits of an environmental condition within which a species can survive.

Limiting factor

An environmental condition that restricts which organisms can survive in a habitat.

Thermoregulation

How the body maintains its internal temperature within a range allowing normal functioning.

Shivering

Involuntary muscle contractions that convert muscle energy into heat; can produce up to five times normal heat output.

Basal metabolic rate (BMR)

The level of metabolism needed to maintain the living state at rest, fasting and in a thermoneutral environment.

Metabolism and temperature regulation

When body temperature falls, metabolism increases to produce heat; when temperature rises, metabolism decreases.

Brown adipose tissue (BAT)

Specialised fat tissue that breaks down fatty acids to produce heat directly, with little ATP production.

Vasoconstriction

Muscles around skin arterioles contract, reducing blood flow to the skin and decreasing heat loss.

Vasodilation

Muscles around skin arterioles relax, increasing blood flow near the skin and increasing heat loss.

Piloerection

Tiny erector pili muscles contract, lifting hair follicles and creating trapped air that insulates the body.

Evaporative cooling

Sweat evaporates from the skin, taking heat energy from nearby blood vessels and cooling the body.

Antifreeze substances

Substances such as glycerol, amino acids and sugars that lower the freezing point of body fluids.

Hibernation

A state of dormancy where heart rate, breathing, metabolism and body temperature decrease to reduce energy requirements.

Countercurrent exchange system

A blood vessel system where warm arterial blood transfers heat to cool venous blood, reducing heat loss from extremities.

Desert environment challenge

Organisms must avoid excessive water loss and overheating, both of which can be deadly.

Limiting factor in deserts

Water, because it is scarce and its supply is unpredictable.

Desert animal adaptations (structural)

Examples include large ears, light-coloured fur and long legs, which reduce heat gain or water loss.

Desert animal adaptations (physiological)

Concentrated urine, surviving without drinking, reduced sweating and tolerating higher body temperatures.

Desert animal adaptations (behavioural)

Nocturnal activity, burrowing, dormancy and migration help avoid heat and conserve water.

Desert plant water uptake

Plants use deep tap roots or shallow horizontal roots to absorb water from available sources.

Desert plant water loss minimisation (structural)

Thick waxy cuticle, fewer or sunken stomata, leaf hairs, reduced leaves, altered leaf orientation and water storage tissue.

Desert plant water loss minimisation (physiological)

Stomata open mainly at night and close during the day to reduce water loss while allowing photosynthesis.

Drought tolerant

A plant that can tolerate a period without water and survive a temporary drought.

Drought resistant

A plant that stores water internally and can live for long periods without water.

Desert plant strategy

Maximise water uptake, minimise water loss and produce drought-resistant seeds.

Cold environment challenge

Life processes require liquid water; freezing can destroy cells, while expanding ice can cause cell rupture.

Cold animal adaptations (structural)

Thick fur, blubber, feathers and compact body shapes reduce heat loss.

Cold animal adaptations (physiological)

Antifreeze substances, hibernation and countercurrent exchange help conserve heat.

Cold animal adaptations (behavioural)

Huddling, hibernation and migration help reduce heat loss or energy requirements.

Cold plant adaptation: preventing ice in cells

Plants increase ion concentration in cytosol, lowering the freezing point so ice forms between cells rather than inside them.

Why ice between cells is preferable

Ice inside cells causes rupture and death; ice between cells leaves cells intact and alive.

Deciduous trees

Trees that drop their leaves during cold, dry winters, reducing water loss and damage from ice or snow.

Key principle: cold plant survival

Plants increase ion concentration to lower freezing point and prevent intracellular ice; deciduous trees drop leaves to reduce winter water loss.

Ecosystem

A living community and the non-living physical surroundings and the interactions both within the community and between the community and its non-living surroundings.

Population

All the individuals of one particular species living in the same area at the same time.

Community

All the populations of various organisms living in the same area at the same time.

Autotrophs (Producers)

Organisms that can manufacture their own organic compounds (like glucose) as their source of energy. Examples: plants, algae, cyanobacteria.

Heterotrophs (Consumers)

Organisms that need to consume organic matter to obtain energy. Can be herbivores, carnivores, omnivores, or detritivores.

Herbivores

Consumers that eat plants. Examples: wallabies, giraffes, algae-eating fish.

Carnivores

Consumers that eat animals. Examples: snakes, numbats, lions, tigers, coral polyps.

Omnivores

Consumers that eat both plants and animals. Examples: humans, crows, chipmunks.

Detritivores

Consumers that eat decomposing matter. Examples: dung beetles, crabs, earthworms.

Decomposers

Organisms that break down dead organic matter into simple inorganic matter. Examples: bacteria, fungi.

Keystone species

A species whose presence in an ecosystem is essential for the maintenance of that ecosystem. Without it, the ecosystem would be dramatically different or cease to exist. Has a disproportionately large impact compared to its abundance.

Keystone species examples (3)

1. Elephants: eat/uproot shrubs, maintaining grassland for herbivores and predators. 2. Seastars: sole predator of mussels, maintaining species diversity. 3. Cassowaries: disperse seeds of rainforest plants through dung.

Predation

One organism (predator) kills and eats another (prey). Predator benefits (+), prey harmed (−). Example: lion kills zebra.

Parasitism

One organism (parasite) lives on/in another (host) and feeds on it without killing it immediately. Parasite benefits (+), host harmed (−). Examples: tapeworm in human, flea on dog, mosquito on human.

Key difference: Parasitism vs Predation

Parasite does NOT kill host immediately; host stays alive and parasite feeds over time. Predator kills prey directly.

Mutualism

Both organisms benefit from the relationship. Both benefit (+ +). Examples: clownfish and sea anemone; bees and flowering plants.

Commensalism

One organism benefits, the other is neither harmed nor benefited. One benefits (+), one unaffected (0). Examples: remora fish on shark; bird building nest in tree.

Amensalism

One organism is harmed, the other is unaffected. One harmed (−), one unaffected (0). Example: antibiotics from fungus kill bacteria.

Competition

Two organisms compete for the same limited resource (food, space, light, water). Both harmed (− −) because both have reduced access to the resource. Types: intraspecies and interspecies.

Intraspecies competition

Competition between individuals of the SAME species for the same resource. Example: two deer fighting for food.