Biology: Characteristics, Levels, and Evidence of Evolution

8 Characteristics of Living Things.1

All living things are made of cells

Levels of Organization in Multicellular Organisms

Cells → Tissues → Organs → Organ systems → Organism

Cell

Smallest unit of life.

Tissue

Group of similar cells that work together to perform a function (e.g., muscle tissue).

Organ

Structure made of different tissues working together (e.g., heart with muscle, connective, and nerve tissue).

Organ System

Group of organs performing major body functions (e.g., circulatory system).

Unicellular Organism

Organism made of a single cell.

Multicellular Organism

Organism made of many specialized cells.

Cell Theory (3 Points)

1) All living things are made of cells 2) Cells are the basic unit of structure and function 3) All cells come from pre-existing cells

Growth

Increase in size or number of cells.

Development

When cells specialize and the organism changes over time.

Metabolism

All chemical reactions that build up or break down materials to provide energy.

Evolution

Change in characteristics within a population of living organisms over many generations.

Microevolution

Small-scale evolutionary change within a species (e.g., bacteria becoming resistant to antibiotics).

Macroevolution

Large-scale evolutionary change over long time periods that produces new species (e.g., whales evolving from land mammals).

Species

Group of organisms that can breed and produce viable, fertile offspring.

Natural Selection

Process where nature selects traits that help survival and reproduction. Requires: Random variations in population, Struggle for existence (selection pressure), Reproduction of the fittest (heritability), Over generations, beneficial traits become more common.

Artificial Selection

Human-controlled breeding to produce desired traits (e.g., dog breeds).

Adaptation

Favorable characteristic/trait an organism is born with that allows better survival and reproduction.

Biological Fitness

Ability of an individual to produce surviving, fertile offspring compared to others.

Evidence for Evolution.1

Biogeography - the presence of unique species on island with no close relative elsewhere, but with close relative on the nearest mainland, suggest that the island species migrated from the mainland and then evolve in isolation

Homologous Structures

Similar anatomical structures from a common ancestor with different functions (e.g., human arm, whale flipper).

Vestigial Structures

Structures once useful but now reduced or without major function (e.g., human appendix, whale pelvis).

Biogeography

Distribution of species across Earth that supports evolutionary relationships (e.g., island species evolving separately from mainland species).

8 Characteristics of Living Things.2

They reproduce

8 Characteristics of Living Things.3

They are based on a universal genetic code (DNA)

8 Characteristics of Living Things.4

They need materials and energy (metabolism)

8 Characteristics of Living Things.5

They respond to their environment ("stimulus and response")

8 Characteristics of Living Things.6

They maintain an internal balance (homeostasis)

8 Characteristics of Living Things.7

They grow and develop

8 Characteristics of Living Things.8

Populations change over time (evolution)

Evidence for Evolution.2

Homologues structures - organs or bones of animals that shows similar structures but may have very different function

Evidence for Evolution.3

Fossil records

Evidence for Evolution.4

Vestigial structure - once useful but now appear to have no purpose

Evidence for Evolution.5

Similarities in development (embryology) e.g. vertebrate animals look very have very similar backbone when developing as embryos

Evidence for Evolution.6

Genetics & biochemistry - similarities in genes and proteins between organisms