Plant Evolution

(This is the online version of the paper booklet available at ticket offices in the Garden.)

This trail supports the University of Cambridge first-year Natural Sciences lecture series in plant evolution.

This trail will introduce you to a selection of plants through evolutionary time, starting with freshwater green algae closely related to land plants. Moving onto land, you will then see living relatives of the early land plants, which have no internal pipework to transport water; they live in damp, shady places.

Around 425 million years ago, plants evolved the ability to transport water, meaning they could grow larger and develop more complex structures. The development of leaves allowed for increased photosynthesis, and seeds enabled survival through conditions unfavourable for the plant itself.

Flowering plants evolved around 140 million years ago, and are the most diverse group in today’s plant kingdom. An evolutionary trend to more specialised flowers has been linked to an increase in diversity of pollinating insects.

Details of the steps necessary for plants to conquer the land, including the key innovations of each of the land plant groups, can be found in the interpretation boards on the Rising Path by the Systematic Beds.

🌿Exciting updates have reshaped our understanding of the land plant phylogenetic tree! Recent research has revealed new insights into plant evolution, and we’ve integrated these findings into the updated tree and trail below. Be sure to check out the video as well – it has a new introduction by Dr Hamish Symington explaining these changes in more detail.🌿

Download the Evolution of Plants trail booklet or map.

You can also view a virtual tour about plant evolution by Prof. Beverley Glover and Dr Hamish Symington.

The life cycle of plants, known as ‘alternation of generations’. Depending on the plant, sporophytes and gametophytes range in size from very few cells to complex organisms.

Animals have two copies of each chromosome in all but a few specialised cells; this is referred to as ‘diploid’. Having one copy of each chromosome per cell is referred to as ‘haploid’.

The visible growth of algae such as Chara is haploid. The haploid stage of a plant’s life is known as the ‘gametophyte’, and eventually produces haploid gametes: sperm and eggs. These fuse to form a diploid zygote; this diploid stage is known as the ‘sporophyte’. In Chara, the sporophyte immediately divides to form haploid spores, which then develop into new haploid gametophyte plants.

Like Chara, the largest phase in the life of a bryophyte is the gametophyte. However, their diploid sporophytes grow to be more complex than a single cell, being patches (in Conocephalum), or small structures (in Porella and mosses) which grow on the surface of the gametophyte.

From the lycophytes onward, the dominant phase of life is the sporophyte. These sporophytes are vascular, meaning they can transport water and nutrients around the plant. This innovation has allowed the expansion in size of plants from the small, feathery spikemosses to the enormous trees visible in the Garden. In these vascular plants, the gametophyte still exists, but has been reduced to around a few hundred cells (in the case of the ferns and horsetails), or even smaller (just a handful of cells in the seed plants).

Details of the steps necessary for plants to conquer the land, including the key innovations of each of the land plant groups, can be found in the interpretation boards on the Rising Path by the Systematic Beds.