2025 Biology Exam Revision Flashcards

Flashcards based on genetics, evolution, adaptations, and ecosystems from lecture notes.

Gamete

Sex cell created by meiosis with half the number of chromosomes (23), only used in reproduction (sperm and egg).

Somatic cell

Diploid cell carrying two sets of genetic material (one from each parent).

Genotype

Unique combination of alleles for a gene inherited from parents.

Phenotype

Physical expression of a genotype (what shows).

Diploid

Cell with two sets of chromosomes, one from each parent.

Zygote

The first cell of an embryo (fertilized egg).

Homozygous

Individuals with two identical alleles (RR or rr).

Heterozygous

Individuals with two non-identical alleles (Rr).

Sex-linked

A trait that’s carried through the X or Y chromosomes.

X-linked

Carried through the X chromosome.

Allele

Type of gene (e.g., an allele for blonde hair).

Deoxyribonucleic Acid

What does DNA stand for?

Name the four nitrogenous bases found in DNA.

Thymine, guanine, adenine, cytosine.

Name the complementary base pairs for the nitrogenous bases in DNA.

A & T, G & C.

Describe the basic structure of DNA.

Made up of nucleotides, two strands twisted around each other (double helix).

Describe the role of DNA.

Carries genetic information necessary for growth, development, and function.

Discuss how the following words link together: Nucleus, DNA, Chromosome, Gene and Protein.

Nucleus contains DNA, organized into chromosomes. Segments of DNA (genes) provide instructions to make proteins that perform essential cell functions.

State the ratio of Mendel’s pea plants when he crossed 2 heterozygous individuals.

3:1

In butterflies, green wings are dominant and white wings are recessive. State the possible genotypes and identify the phenotype they represent.

GG (Green), Gg (Green), gg (White)

State how many chromosomes a human somatic cell has.

46

State how many chromosomes a human gamete cell has.

23

Discuss what mitosis and meiosis have in common.

Processes of cell duplication, contain a nucleus, involve cell division, phase names are the same.

State the main function of mitosis.

Repair and growth, produce 2 identical daughter cells.

State the main function of meiosis.

Reproduction, producing gametes (sperm or egg cells), 4 unique daughter cells.

State the genotypes of male and female mammals.

XX and XY.

Explain how the sex of a human child/mammal offspring is determined.

A female has XX chromosomes; a male has XY chromosomes. A female always passes an X chromosome down, but the male will pass down either X or Y.

Explain what a karyotype is.

A display of chromosome pairs of a cell arranged by size and shape.

Explain what a pedigree is.

A chart that shows how a trait and genes are passed down through generations.

Is albinism a dominant trait or a recessive trait?

Recessive trait.

State the genotypes of the following people from the albinism pedigree: Bill, Don, Karen, Brian, Sam

Based on the pedigree LEFT: Bill (aa), Don (Aa), Karen (aa), Brian (Aa), Sam (Aa)

Use the polydactyly pedigree. State if polydactyly is a dominant trait or a recessive trait.

Right pedigree: Dominant Trait

Define allele.

Variant form of a gene.

Define mutations and discuss how they are caused.

Alterations in the genetic material; caused by various factors like radiation or chemicals.

Explain who Charles Darwin was.

Charles Darwin was an English naturalist, geologist and biologist, best known for his contributions to evolutionary biology.

Explain what Darwin’s theory on evolution was.

The theory of evolution is based on the idea that all species are related and gradually change over time.

Explain how Gondwana, Laurasia, and Pangaea linked.

Gondwana, Laurasia, and Pangaea were supercontinents in Earth's past. Pangaea split into Gondwana and Laurasia.

Define marsupials. State where they found in the world. Explain this distribution.

Marsupials are mammals that carry their young in a pouch. They are found mainly in Australia and the Americas. This distribution is due to continental drift.

Explain the concept of plate tectonics.

Plate tectonics is the theory that Earth's outer shell is divided into several plates that glide over the mantle, the rocky inner layer above the core.

Discuss how plate tectonics supports the theory of evolution.

Plate tectonics supports the theory of evolution by explaining the distribution of species across different continents, such as marsupials.

Define fossils.

Fossils are the preserved remains or traces of animals, plants, and other organisms from the past.

Define living fossils.

Living fossils are extant species that closely resemble extinct species known from the fossil record.

Define the following terms: species, speciation, hybrid.

Species: a group of living organisms consisting of similar individuals capable of exchanging genes or interbreeding. Speciation: the formation of new and distinct species in the course of evolution. Hybrid: the offspring of two plants or animals of different species or varieties.

Describe the stages of speciation.

Geographic isolation, divergence, reproductive isolation.

Explain the theory of natural selection.

Natural selection is the differential survival and reproduction of individuals due to differences in phenotype.

Describe how the peppered moths changed over time. Justify your answer.

The peppered moths changed from predominantly light-colored to predominantly dark-colored due to industrial pollution, which darkened tree bark.

Define divergent evolution.

Divergent evolution is the accumulation of differences between groups which can lead to the formation of new species.

Define convergent evolution.

Convergent evolution is the process whereby organisms not closely related independently evolve similar traits as a result of having to adapt to similar environments or ecological niches.

Define homologous structures. Give an example.

Homologous structures are structures in different species that are similar because of common ancestry. An example is the forelimbs of humans, bats, and whales.

Define analogous structures. Give an example.

Analogous structures are structures in different species that perform the same function, but have evolved separately. An example is the wings of insects and birds.

State the type of evolution analogous structures are linked to.

Convergent evolution.

State the type of evolution homologous structures are linked to.

Divergent evolution.

Define adaptation.

An adaptation is a trait with a functional role in the life history of an organism, maintained and evolved by means of natural selection.

Define ecosystem.

An ecosystem is a geographic area where plants, animals, and other organisms, as well as weather and landscape, work together to form a bubble of life.

Define habitat.

A habitat is the natural home or environment of an animal, plant, or other organism.

Define range.

The range of a species is the geographic area where that species can be found.

State the difference between biotic and abiotic factors.

Biotic factors are living things in an ecosystem, while abiotic factors are non-living things.

List 3 examples of biotic and abiotic factors.

Biotic: plants, animals, bacteria. Abiotic: sunlight, water, temperature.

Explain the difference between a population and a community.

A population is a group of individuals of the same species living in an area, while a community is a group of different species living in an area.

Explain the difference between an autotroph and a heterotroph.

An autotroph is an organism that can produce its own food, while a heterotroph is an organism that consumes other organisms for food.

Explain the difference between a producer and a consumer.

A producer is an organism that makes its own food (autotroph), while a consumer is an organism that eats other organisms (heterotroph).

Define trophic level.

A trophic level is the position an organism occupies in a food web.

State which trophic level/s the following types of organisms would be found. Justify your answers: i. Producers ii. Herbivore iii. Carnivore iv. Decomposer

Producers: 1st trophic level. Herbivore: 2nd trophic level. Carnivore: 3rd or higher trophic level. Decomposer: can span multiple trophic levels.

Explain if an organism can occupy more than one trophic level in an ecosystem.

Yes, an organism can occupy more than one trophic level if it has a varied diet.

State the 2 essential requirements for a food web to be self-sufficient.

A constant source of energy and nutrient cycling.

State the source of energy for most ecosystems.

The sun.

State how energy is lost from an ecosystem.

Heat.

Define food chain and food web.

A food chain is a linear sequence of organisms through which nutrients and energy pass as one organism eats another. A food web is a network of interconnected food chains.

State what the arrows represent in a food chain and food web.

Flow of energy and nutrients.

State what the consequences of removing a producer from an ecosystem.

Disruption of the food web, loss of energy flow, and potential collapse of the ecosystem.

Define competitor.

An organism that reduces the availability of resources to other organisms that share the same habitat (e.g., food, water, sunlight).