Diversity of organisms

A group of organisms that can **interbreed** and produce **fertile offspring**.

Defining a species by the ability to **interbreed** and produce **fertile offspring**.

Young that are themselves **able to reproduce**.

The offspring of a cross between **two different species** (e.g. a mule).

**Unable to reproduce** — cannot produce offspring of its own.

**No** — they produce a **mule**, which is **sterile**, so they are different species.

It leaves out that the offspring must be **fertile** — sterile young mean the parents are different species.

**Yes** — they can interbreed and give fertile pups; breed differences are just variation within one species.

An organism's full set of **chromosomes**, shown by their **number, size and shape**.

**Matching** chromosome number/pattern supports the **same** species; clearly **different** karyotypes suggest different species.

Organisms that **do not reproduce sexually** (e.g. bacteria) and **fossils**.

A **mule** — a sterile **hybrid**.

The system of naming each species with a **two-part Latin name**: **genus + species**.

The **first** word (it is capitalised), e.g. **Panthera** in **Panthera leo**.

The **second** word (it is lower-case); it only has meaning alongside its genus.

A group of **closely related species** — the first word of a scientific name.

In **italics**, with the genus **capitalised** and the species **lower-case**.

**Underline** each word (since you can't italicise by hand); genus still capitalised, species lower-case.

**Carl Linnaeus**, in the 1700s.

Linnaeus's idea of grouping organisms into species by their **shared physical features / appearance**.

They are **more closely related** than two species placed in **different genera**.

**Closely related** — they share the genus **Felis** (the same first word).

It has **no meaning without its genus** — different genera can reuse the same species word.

Common names vary between languages and regions; a binomial name is **one agreed name** for each species worldwide.

**Plants, animals, fungi and protists.**

An organism whose cells have a **nucleus** (and membrane-bound organelles).

**Cellulose.**

**Chitin.**

An organism that **makes its own food** from simple inorganic molecules (e.g. by photosynthesis).

An organism that obtains food by **taking in organic molecules** made by other organisms.

An organism that can feed as an **autotroph OR a heterotroph**, depending on conditions.

Heterotrophic feeding where food is taken **into the body and digested internally** (as animals do).

Heterotrophic feeding where enzymes digest **dead matter outside** the body, then the products are absorbed (as fungi do).

**Plants** (cellulose) and **fungi** (chitin) — same idea, different material.

**Autotrophic** — chloroplasts let it make its own food by photosynthesis.

They are the **'everything else'** eukaryotes — mostly **unicellular** and not fitting plants, animals or fungi.

A feature that **tells the group apart** from others (e.g. feathers for birds), not just any feature the organism has.

**Fur/hair** and **feeding young on milk** (from mammary glands).

**Feathers** and a **beak** (no teeth); they also lay hard-shelled eggs.

**Scales**, **gills** and **fins**; they live in water.

**Moist smooth skin**; they live partly in water and lay jelly-covered eggs in water.

Flowering plants have **true roots, vascular tissue and flowers/seeds**; mosses have **none** and reproduce by **spores**.

By **spores** — they have no flowers or seeds.

**Cnidarians** (e.g. jellyfish, sea anemones).

A **soft body**, often protected by a **shell** (e.g. snail, octopus).

A hard **exoskeleton** and **jointed legs** (e.g. insects, spiders, crabs).

A long body built from many similar **ring-like segments** (e.g. earthworm).

An animal with a **backbone** (a column of bones along its back).

A **common ancestor**. Groups meeting at a **more recent node** are **more closely related**.

**Molecular evidence** — comparing the **amino-acid sequence** of a shared protein (e.g. myoglobin) or the **DNA base sequence**. Fewer differences ⇒ more recent common ancestor.

They share **characteristics inherited from a common ancestor** — the shared rank reflects a recent common ancestry.

An identification tool made of **paired either/or choices** about observable features, each leading to another step or to an organism's **name**.

**Split into two** — every step offers exactly **two** opposite choices.

At **Step 1** (the top), then follow the matching choices in order.

A characteristic you can **see or measure** directly — e.g. legs, shell, scales, wings.

The key has reached the point that **names (identifies)** the organism.

**Two** — a pair of opposite either/or statements.

So every organism fits **exactly one** side at each step, with **no overlap**.

Habitat is **not a body feature** — a key must use features you can **observe** on the organism.

Follow **only the choice that matches** your organism, then go to the step or name it points to.

It shows the **correct path** for the marks and helps you **avoid careless slips**.

From its **observable features** — follow the key; never guess from the name.

One **numbered pair** of opposite statements; you pick the one that matches the organism.

A living organism whose **whole body is a single cell**.

A **life process every living organism must carry out** to stay alive (e.g. nutrition, response, reproduction).

**Nutrition, metabolism, growth, response, excretion, homeostasis, reproduction.**

It has **no tissues or organs** to share the work — the **one cell** must do everything itself.

**Nutrition** — taking in nutrients/food.

**Homeostasis** — it pumps out excess water to keep the internal water balance stable.

The water it removes entered by **osmosis** and is **not a metabolic waste** — excretion removes metabolic waste like CO₂.

**Excretion** — removing a waste product of metabolism.

**Response** — reacting to a stimulus in the surroundings.

Reproduction in which **one cell divides into two identical cells**.

**Reproduction** (by binary fission).

Any two of: **Paramecium, Amoeba, Euglena, Chlamydomonas, bacteria.**